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human
Each edge length of a rectangular solid is a prime number. If the volume of the rectangular solid is 385 cubic units, what is the total surface area, in square units, of the rectangular solid?
gpt
Prime factorize $385$ as $5\cdot7\cdot 11$. The surface area of a rectangular solid having side lengths of 5, 7, and 11 units is $2(5\cdot7+7\cdot11+11\cdot5)=\boxed{334}$ square units.
human
A spiral staircase turns $270^\circ$ as it rises 10 feet. The radius of the staircase is 3 feet. What is the number of feet in the length of the handrail? Express your answer as a decimal to the nearest tenth.
gpt
The handrail encases a right circular cylinder with radius 3 feet and height 10 feet. Its lateral area is a rectangle with height 10 feet and width equal to its base circumference, or $2\pi\cdot 3 = 6\pi$ feet. A staircase that turns $360^\circ$ would, when unrolled and lain flat, span the diagonal of this rectangle....
human
Triangle $ABC$ is a right triangle with legs $AB$ and $AC$. Points $X$ and $Y$ lie on legs $AB$ and $AC$, respectively, so that $AX:XB = AY:YC = 1:2$. If $BY = 16$ units, and $CX = 28$ units, what is the length of hypotenuse $BC$? Express your answer in simplest radical form.
gpt
Let $AB = x$ and $AC = y$. Then we can write two Pythagorean equations from the information given: $(x/3)^2 + y^2 = 28^2$ and $x^2 + (y/3)^2 = 16^2$. These equations become $x^2/9 + y^2 = 784$ and $x^2 + y^2/9 = 256$. Multiplying them both by 9, we get $x^2 + 9y^2= 7056$ and $9x^2 + y^2 = 2304$. Now we add the two equa...
human
The sides of a triangle have lengths of $15$, $20$, and $25$. Find the length of the shortest altitude.
gpt
First notice that this is a right triangle, so two of the altitudes are the legs, whose lengths are $15$ and $20$. The third altitude, whose length is $x$, is the one drawn to the hypotenuse. The area of the triangle is $\frac{1}{2}(15)(20) = 150$. Using 25 as the base and $x$ as the altitude, we have $$ \frac{1}{2}(...
human
The area of one lateral face of a right pyramid with an equilateral triangular base is 75 square meters. If the slant height is 30 meters, what is the length of the side of its base, in meters?
gpt
Let $s$ represent the sidelength of the equilateral triangular base. Each face of the pyramid has an area of $\frac{1}{2}bh=75$, where $b$ is the sidelength of the base and $h$ is the slant height of 30 meters. We have $$75=\frac{1}{2}s(30)=15s.$$So, $s=5$ and the sidelength of the base is $\boxed{5}$ meters.
human
Altitudes $\overline{AX}$ and $\overline{BY}$ of acute triangle $ABC$ intersect at $H$. If $\angle BAC = 61^\circ$ and $\angle ABC = 73^\circ$, then what is $\angle CHX$?
gpt
First, we build a diagram: [asy] size(150); defaultpen(linewidth(0.8)); pair B = (0,0), C = (3,0), A = (1,2), P = foot(A,B,C), Q = foot(B,A,C),H = intersectionpoint(B--Q,A--P); draw(A--B--C--cycle); draw(A--P^^B--Q); pair Z; Z = foot(C,A,B); draw(C--Z); label("$A$",A,N); label("$B$",B,W); label("$C$",C,E); label("$X$"...
human
A triangle with side lengths in the ratio 3:4:5 is inscribed in a circle of radius 3. What is the area of the triangle? Provide your answer as a decimal rounded to the nearest hundredth.
gpt
Let the sides of the triangle have lengths $3x$, $4x$, and $5x$. The triangle is a right triangle, so its hypotenuse is a diameter of the circle. Thus $5x=2\cdot 3=6$, so $x=6/5$. The area of the triangle is \[ \frac{1}{2}\cdot 3x\cdot 4x =\frac{1}{2}\cdot \frac{18}{5}\cdot \frac{24}{5} =\frac{216}{25}=\boxed{8.64}....
human
A hexagon inscribed in a circle has three consecutive sides, each of length 3, and three consecutive sides, each of length 5. The chord of the circle that divides the hexagon into two trapezoids, one with three sides, each of length 3, and the other with three sides, each of length 5, has length equal to $m/n$, where $...
gpt
In hexagon $ABCDEF$, let $AB=BC=CD=3$ and let $DE=EF=FA=5$. Since arc $BAF$ is one third of the circumference of the circle, it follows that $\angle BCF = \angle BEF=60^{\circ}$. Similarly, $\angle CBE =\angle CFE=60^{\circ}$. Let $P$ be the intersection of $\overline{BE}$ and $\overline{CF}$, $Q$ that of $\overline{BE...
human
In the diagram, $\triangle PQR$ is right-angled at $P$ and has $PQ=2$ and $PR=2\sqrt{3}$. Altitude $PL$ intersects median $RM$ at $F$. What is the length of $PF$? [asy] draw((0,0)--(10,0)--(0,10*sqrt(3))--cycle); draw((0,0)--(7.5,4.33)); draw((0,10*sqrt(3))--(5,0)); draw((6.68,3.86)--(7.17,3.01)--(7.99,3.49)); label(...
gpt
Since $PQ=2$ and $M$ is the midpoint of $PQ$, then $PM = MQ =\frac{1}{2}(2)=1$. Since $\triangle PQR$ is right-angled at $P$, then by the Pythagorean Theorem, \[ RQ = \sqrt{PQ^2+PR^2} = \sqrt{2^2+(2\sqrt{3})^2}=\sqrt{4+12}=\sqrt{16}=4. \](Note that we could say that $\triangle PQR$ is a $30^\circ$-$60^\circ$-$90^\cir...
human
An equilateral triangle has sides 8 units long. An equilateral triangle with sides 4 units long is cut off at the top, leaving an isosceles trapezoid. What is the ratio of the area of the smaller triangle to the area of the trapezoid? Express your answer as a common fraction.
gpt
Connect the midpoints of the sides of the equilateral triangle as shown. The triangle is divided into four congruent equilateral triangles, and the isosceles trapezoid is made up of 3 of these 4 triangles. Therefore, the ratio of the area of one of the triangles to the area of the trapezoid is $\boxed{\frac{1}{3}}$. ...
human
The first square below is in position ABCD. After rotating the square 90 degrees clockwise about its center point, the second square is in position DABC, as shown. Next, square DABC is reflected over its vertical line of symmetry, resulting in the third square in position CBAD. If the pattern of alternately rotating 90...
gpt
If we extend the pattern, we note that the rearrangements of the vertices return to the original order after four steps: ABCD $\rightarrow$ DABC $\rightarrow$ CBAD $\rightarrow$ DCBA $\rightarrow$ ABCD. Thus, since the sequence repeats, we know that every fourth rearrangement will be of the form DCBA. The 2007th square...
human
Suppose that we have a right triangle $ABC$ with the right angle at $B$ such that $AC = \sqrt{61}$ and $AB = 5.$ A circle is drawn with its center on $AB$ such that the circle is tangent to $AC$ and $BC.$ If $P$ is the point where the circle and side $AC$ meet, then what is $CP$?
gpt
Since we have a right triangle, we can see that any circle with center on $AB$ is tangent to $BC$ at the right angle itself, or $B.$ Since $P$ is the point at which $AC$ and the circle meet, we see that $CP$ is a tangent from $C,$ as is $BC.$ That means $BC = CP.$ We can easily find $BC$ via the Pythagorean Theorem, as...
human
$ABCDE$ is a regular pentagon. $AP$, $AQ$ and $AR$ are the perpendiculars dropped from $A$ onto $CD$, $CB$ extended and $DE$ extended, respectively. Let $O$ be the center of the pentagon. If $OP = 1$, then find $AO + AQ + AR$. [asy] unitsize(2 cm); pair A, B, C, D, E, O, P, Q, R; A = dir(90); B = dir(90 - 360/5...
gpt
To solve the problem, we compute the area of regular pentagon $ABCDE$ in two different ways. First, we can divide regular pentagon $ABCDE$ into five congruent triangles. [asy] unitsize(2 cm); pair A, B, C, D, E, O, P, Q, R; A = dir(90); B = dir(90 - 360/5); C = dir(90 - 2*360/5); D = dir(90 - 3*360/5); E = dir...
human
A right cylinder with a base radius of 3 units is inscribed in a sphere of radius 5 units. The total volume, in cubic units, of the space inside the sphere and outside the cylinder is $W\pi$. Find $W$, as a common fraction.
gpt
To begin, we need to visualize the cylinder inscribed in the sphere. We can draw the cylinder as shown: [asy] size(150); draw((0,0)--(6,0)--(6,8)--(0,8)--cycle,linewidth(.7)); draw((0,8)--(6,0),linewidth(.7)); draw((0,0)..(3,-1.5)..(6,0),linewidth(.7)); draw((0,0)..(3,1.5)..(6,0),linewidth(.7)); draw((0,8)..(3,9.5)..(...
human
In the diagram, $\triangle ABE$, $\triangle BCE$ and $\triangle CDE$ are right-angled, with $\angle AEB=\angle BEC = \angle CED = 60^\circ$, and $AE=24$. [asy] pair A, B, C, D, E; A=(0,20.785); B=(0,0); C=(9,-5.196); D=(13.5,-2.598); E=(12,0); draw(A--B--C--D--E--A); draw(B--E); draw(C--E); label("A", A, N); label("B",...
gpt
We find $CE$ by first finding $BE$. Since $AE = 24$ and $\angle AEB = 60^\circ$ and $AEB$ is a right triangle, then we can see that $AE$ is the hypotenuse and $BE$ is the shorter leg, so $BE = \dfrac{1}{2} \cdot 24 = 12.$ Likewise, since $BE = 12$ and $\angle BEC = 60^\circ$, then $CE = \dfrac{1}{2} \cdot 12 = \boxed...
human
The radius of a sphere is $p$ units and the radius of a hemisphere is $2p$ units. What is the ratio of the volume of the sphere to the volume of the hemisphere?
gpt
The volume of the sphere is \[\frac{4}{3}\pi p^3\] and the volume of the hemisphere is \[\frac{1}{2}\cdot \frac{4}{3}\pi (2p)^3 = \frac{4}{3}\pi p^3 \cdot 4.\] Thus the ratio of the volume of the sphere to the volume of the hemisphere is $\boxed{\frac{1}{4}}$.
human
Triangles $ABC$ and $ADE$ have areas $2007$ and $7002,$ respectively, with $B=(0,0), C=(223,0), D=(680,380),$ and $E=(689,389).$ What is the sum of all possible $x$-coordinates of $A$?
gpt
Let $h$ be the length of the altitude from $A$ in $\triangle ABC$. Then \[ 2007=\frac{1}{2}\cdot BC\cdot h=\frac{1}{2}\cdot 223\cdot h, \]so $h=18$. Thus $A$ is on one of the lines $y=18$ or $y=-18$. [asy] unitsize(1 cm); pair B, C, D, E; B = (0,0); C = (2,0); D = (7,3); E = (8,4); draw((-1.5,0.5)--(6,0.5),dashed)...
human
Right triangle $ABC$ has one leg of length 6 cm, one leg of length 8 cm and a right angle at $A$. A square has one side on the hypotenuse of triangle $ABC$ and a vertex on each of the two legs of triangle $ABC$. What is the length of one side of the square, in cm? Express your answer as a common fraction. [asy] defaul...
gpt
Let $s$ be the side length of the square. Also let $D$ be the vertex of the square on side $AC$, and let $E$ be the vertex of the square on side $AB$. Let $F$ and $G$ be the feet of the altitudes from $D$ and $A$ to $BC$, respectively. Let $x$ be the length of $AD$. [asy] unitsize(0.5 cm); pair A, B, C, D, E, F, G, H...
human
Let $P$ be a point inside triangle $ABC$. Let $G_1$, $G_2$, and $G_3$ be the centroids of triangles $PBC$, $PCA$, and $PAB$, respectively. If the area of triangle $ABC$ is 18, then find the area of triangle $G_1 G_2 G_3$. [asy] import geometry; unitsize(2 cm); pair A, B, C, P; pair[] G; A = (1,3); B = (0,0); C = ...
gpt
Let $M_1$, $M_2$, and $M_3$ be the midpoints of $AP$, $BP$, and $CP$, respectively. Then as a midline in triangle $PBC$, $M_2 M_3$ is parallel to $BC$, and half the length of $BC$. [asy] import geometry; unitsize(2 cm); pair A, B, C, P; pair[] G, M; A = (1,3); B = (0,0); C = (4,0); P = (2,1); G[1] = (P + B + C)/3;...
human
The figure shows a square in the interior of a regular hexagon. The square and regular hexagon share a common side. What is the degree measure of $\angle ABC$? [asy] size(150); pair A, B, C, D, E, F, G, H; A=(0,.866); B=(.5,1.732); C=(1.5,1.732); D=(2,.866); E=(1.5,0); F=(.5,0); G=(.5,1); H=(1.5,1); draw(A--B); draw(B...
gpt
Label the lower right corner of the square point $D$ and the lower left corner $E$. The interior angles of a regular hexagon are 120 degrees and the interior angles of a square are 90 degrees. Thus, $m\angle BDC=m \angle BDE - m\angle CDE=120^\circ - 90^\circ = 30^\circ$. In addition, because the square and regular hex...
human
A cube has a surface area of 216 square centimeters. What is the volume of the cube, in cubic centimeters?
gpt
There are 6 faces to a cube, meaning that each face has area 36, and the edge has length 6, for a total volume of $6^3 = \boxed{216}$ for the cube.
human
What is the diameter of the circle inscribed in triangle $ABC$ if $AB = 11,$ $AC=6,$ and $BC=7$? Express your answer in simplest radical form.
gpt
Let $d$ be the diameter of the inscribed circle, and let $r$ be the radius of the inscribed circle. Let $s$ be the semiperimeter of the triangle, that is, $s=\frac{AB+AC+BC}{2}=12$. Let $K$ denote the area of $\triangle ABC$. Heron's formula tells us that \begin{align*} K &= \sqrt{s(s-AB)(s-AC)(s-BC)} \\ &= \sqrt{12\c...
human
In square $ABCD$, $AD$ is 4 centimeters, and $M$ is the midpoint of $\overline{CD}$. Let $O$ be the intersection of $\overline{AC}$ and $\overline{BM}$. What is the ratio of $OC$ to $OA$? Express your answer as a common fraction. [asy] size (3cm,3cm); pair A,B,C,D,M; D=(0,0); C=(1,0); B=(1,1); A=(0,1); draw(A--B--...
gpt
First we draw diagonal $\overline{BD}$, and let the diagonals intersect at $T$, as shown: [asy] size (4cm,4cm); pair A,B,C,D,M; D=(0,0); C=(1,0); B=(1,1); A=(0,1); draw(A--B--C--D--A); M=(1/2)*D+(1/2)*C; draw(B--M); draw(A--C); label("$A$",A,NW); label("$B$",B,NE); label("$C$",C,SE); label("$D$",D,SW); label(...
human
A cone has a volume of $12288\pi$ cubic inches and the vertex angle of the vertical cross section is 60 degrees. What is the height of the cone? Express your answer as a decimal to the nearest tenth. [asy] import markers; size(150); import geometry; draw(scale(1,.2)*arc((0,0),1,0,180),dashed); draw(scale(1,.2)*arc((0,...
gpt
The cross section of the cone is an equilateral triangle. The ratio of the base to the height of an equilateral triangle is 1 to $\sqrt{3}/2$. In terms of the radius, $r$, the base is $2r$ and the height is $2r\sqrt{3}/2$, or $r\sqrt{3}$. Since we know the volume of the cone, we can use the volume formula and solve the...
human
Triangle $ABC$ has vertices with coordinates $A(2,3),$ $B(7,8),$ and $C(-4,6)$. The triangle is reflected about line $L$. The image points are $A'(2,-5),$ $B'(7,-10),$ and $C'(-4,-8)$. What is the equation of line $L$?
gpt
Since only the $y$ portions of the coordinates move, we know that the line of reflection must be a horizontal line. Now we just need to find the midpoint between an original point and its reflected image to pinpoint the location of the line. The $y$-coordinate of point $A$ is 3 and the $y$-coordinate of $A'$ is $-5$; t...
human
In rectangle $ABCD$, $P$ is a point on $BC$ so that $\angle APD=90^{\circ}$. $TS$ is perpendicular to $BC$ with $BP=PT$, as shown. $PD$ intersects $TS$ at $Q$. Point $R$ is on $CD$ such that $RA$ passes through $Q$. In $\triangle PQA$, $PA=20$, $AQ=25$ and $QP=15$. Find $SD$. (Express your answer as a common fracti...
gpt
We have $\angle B = \angle PTQ$ and $\angle TPQ = 180^\circ - \angle QPA - \angle APB = 90^\circ - \angle APB = \angle BAP$. Therefore, $\triangle BAP \sim \triangle TPQ$. Since $AB/AP = 4/5$, triangles $BAP$ and $PTQ$ are $\{3,4,5\}$ right triangles, and we have $TQ = \frac35(15) = 9$ and $TP = \frac45(15)=12$. Sin...
human
Triangle $ABC$ has vertices $A(0, 8)$, $B(2, 0)$, $C(8, 0)$. A line through $B$ cuts the area of $\triangle ABC$ in half; find the sum of the slope and $y$-intercept of this line.
gpt
The line through $B$ that cuts the area of $\triangle ABC$ in half is the median -- that is, the line through $B$ and the midpoint $M$ of $\overline{AC}$. (This line cuts the area of the triangle in half, because if we consider $\overline{AC}$ as its base, then the height of each of $\triangle AMB$ and $\triangle CMB$...
human
The vertices of a $3 - 4 - 5$ right triangle are the centers of three mutually externally tangent circles, as shown. What is the sum of the areas of these circles? [asy]unitsize(1cm); draw(Circle((1.8,2.4),1),linewidth(0.7)); draw(Circle((0,0),2),linewidth(0.7)); draw(Circle((5,0),3),linewidth(0.7)); draw((0,0)--(5,...
gpt
Let $r$, $s$, and $t$ be the radii of the circles centered at $A$, $B$, and $C$, respectively. Then $r+s=3$, $r+t=4$, and $s+t=5$. Adding these three equations gives $2(r+s+t) = 12$, so $r+s+t = 6$. Combining this with the original three equations, we get $r=1$, $s=2$, and $t=3$. Thus the sum of the areas of the circ...
human
Square $ABCD$ has side length $1$ unit. Points $E$ and $F$ are on sides $AB$ and $CB$, respectively, with $AE = CF$. When the square is folded along the lines $DE$ and $DF$, sides $AD$ and $CD$ coincide and lie on diagonal $BD$. The length of segment $AE$ can be expressed in the form $\sqrt{k}-m$ units. What is the ...
gpt
We start by drawing a diagram. When the paper is folded, sides $AD$ and $CD$ coincide on the longer dashed line, and points $A$ and $C$ meet at $G$, as you can see below. [asy] draw((0,0)--(1,0)--(1,1)--(0,1)--cycle); draw((0,0)--(1,.4)); draw((0,0)--(.4,1)); draw((1,.4)--(.4,1),dashed); draw((0,0)--(.7,.7),dashed); ...
human
Rectangle $ABCD$ is inscribed in triangle $EFG$ such that side $AD$ of the rectangle is on side $EG$ of the triangle, as shown. The triangle's altitude from $F$ to side $EG$ is 7 inches, and $EG = 10 \text{ inches}$. The length of segment $AB$ is equal to half the length of segment $AD$. What is the area of rectangle $...
gpt
Suppose that the altitude from $F$ to $EG$ intersects $EG$ at point $H$. Then $\triangle EAB \sim \triangle EHF$, and we have that $\frac{HE}{HF} = \frac{AE}{AB}$. Also, $\triangle GDC \sim GHF$, and $\frac{HG}{HF} = \frac{DG}{DC}$. Adding these equalities, we find that $\frac{HE + HG}{HF} = \frac{AE + DG}{AB}$, sin...
human
$A$, $B$, $C$, and $D$ are points on a circle, and segments $\overline{AC}$ and $\overline{BD}$ intersect at $P$, such that $AP=8$, $PC=1$, and $BD=6$. Find $BP$, given that $BP < DP.$ [asy] unitsize(0.6 inch); draw(circle((0,0),1)); draw((-0.3,0.94)--(0.3,-0.94)); draw((-0.7,-0.7)--(0.7,-0.7)); label("$A$",(-0.3,0...
gpt
Writing $BP=x$ and $PD=6-x$, we have that $BP < 3$. Power of a point at $P$ gives $AP \cdot PC = BP \cdot PD$ or $8=x(6-x)$. This can be solved for $x=2$ and $x=4$, and we discard the latter, leaving $BP = \boxed{2}$.
human
A rectangular prism measures 10-inches by 20-inches by 10-inches. What is the length, in inches, of the diagonal connecting point A and point B? Express your answer in simplest radical form. [asy] unitsize(0.75cm); defaultpen(linewidth(0.7pt)+fontsize(10pt)); dotfactor=4; draw((0,1)--(1,1)--(1,0)--(0,0)--(0,1)--(1,2)-...
gpt
Let $D$ be the vertex opposite $B$ on the bottom face, and let $C$ be one of the other two vertices on the bottom face. Because $BCD$ is a right triangle, we can use the Pythagorean theorem to get $BD=\sqrt{10^2+20^2}$. Then applying the Pythagorean theorem to right triangle $BDA$, we find \begin{align*} AB&=\sqrt{10...
human
Square $ABCD$ has area $200$. Point $E$ lies on side $\overline{BC}$. Points $F$ and $G$ are the midpoints of $\overline{AE}$ and $\overline{DE}$, respectively. Given that quadrilateral $BEGF$ has area $34$, what is the area of triangle $GCD$?
gpt
We begin by drawing a diagram: [asy] size(5cm); pair a=(0,1); pair b=(1,1); pair c=(1,0); pair d=(0,0); pair e=(1,.82); pair f=(a+e)/2; pair g=(d+e)/2; fill(b--e--g--f--cycle,gray); fill(g--c--d--cycle,pink); dot(a);dot(b);dot(c);dot(d);dot(e);dot(f);dot(g); draw(a--b--c--d--a); draw(a--e--d); draw(e--g--f--b); draw(g-...
human
The hypotenuse of a right triangle whose legs are consecutive whole numbers is 29 units. What is the sum of the lengths of the two legs?
gpt
Let's call the length of the shorter leg $x$. Then the length of the longer leg is $x + 1$. Using the Pythagorean Theorem, we write the equation $x^2 + (x + 1)^2 = 29^2$ and solve for $x$. Expanding $(x + 1)^2$, we get $x ^2 + x^2 + 2x + 1 = 841$. This can be simplified to $2x^2 + 2x = 840$, or $x^2 + x = 420$. Factori...
human
Let $\triangle ABC$ be a right triangle such that $B$ is a right angle. A circle with diameter of $BC$ meets side $AC$ at $D.$ If $AD = 1$ and $BD = 4,$ then what is $CD$?
gpt
We might try sketching a diagram: [asy] pair pA, pB, pC, pO, pD; pA = (-5, 0); pB = (0, 0); pC = (0, 20); pO = (0, 10); pD = (-80/17, 20/17); draw(pA--pB--pC--pA); draw(pD--pB); draw(circle(pO, 10)); label("$A$", pA, SW); label("$B$", pB, S); label("$C$", pC, N); label("$D$", pD, NE); [/asy] Since $BC$ is a diameter of...
human
Suppose $\cos R = \frac{4}{9}$ in the diagram below. What is $QS$? [asy] pair Q,R,S; S = (0,0); Q = (sqrt(65),0); R = (sqrt(65),-4); draw(S--Q--R--S); draw(rightanglemark(S,Q,R,13)); label("$S$",S,NW); label("$Q$",Q,NE); label("$R$",R,SE); label("$9$",(R+S)/2,SW); [/asy]
gpt
Since $\cos R = \frac{4}{9}$ and $\cos R = \frac{QR}{RS}=\frac{QR}{9}$, we have $\frac{QR}{9} = \frac{4}{9}$, so $QR = 4$. Then, by the Pythagorean Theorem, $QS = \sqrt{RS^2 - QR^2} = \sqrt{81-16} = \boxed{\sqrt{65}}$.
human
Three faces of a right rectangular prism have areas of 48, 49 and 50 square units. What is the volume of the prism, in cubic units? Express your answer to the nearest whole number.
gpt
If the length, width, and height of the rectangular prism are $a$, $b$, and $c$, then we are given $ab=48$, $bc=49$, and $ac=50$. Since we are looking for $abc$, the volume of the rectangular prism, we multiply these three equations to find \begin{align*} (ab)(bc)(ac)&=48\cdot49\cdot50 \implies \\ a^2b^2c^2&=48\cdot49...
human
Circles centered at $A$ and $B$ each have radius 2, as shown. Point $O$ is the midpoint of $\overline{AB}$, and $OA=2\sqrt{2}$. Segments $OC$ and $OD$ are tangent to the circles centered at $A$ and $B$, respectively, and $\overline{EF}$ is a common tangent. What is the area of the shaded region $ECODF$? [asy]unitsiz...
gpt
Rectangle $ABFE$ has area $AE\cdot AB=2\cdot 4\sqrt{2}=8\sqrt{2}$. Right triangles $ACO$ and $BDO$ each have hypotenuse $2\sqrt{2}$ and one leg of length 2. [asy]unitsize(1cm); pair A,B,C,D,G,F,O; A=(-2.8,0); B=(2.8,0); C=(-1.4,1.4); D=(1.4,1.4); G=(-2.8,2); F=(2.8,2); O=(0,0); draw(A--B,linewidth(0.8)); draw(G--F,li...
human
In $\triangle ABC$, we have $AC=BC=7$ and $AB=2$. Suppose that $D$ is a point on line $AB$ such that $B$ lies between $A$ and $D$ and $CD=8$. What is $BD$?
gpt
Let $\overline{CH}$ be an altitude of $\triangle ABC$. Applying the Pythagorean Theorem to $\triangle CHB$ and to $\triangle CHD$ produces \[ 8^2 - (BD +1)^2 = CH^2 = 7^2 - 1^2 = 48, \quad \text{so} \quad (BD+1)^2 = 16. \] Thus $BD = \boxed{3}$. [asy] unitsize(0.5cm); pair A,B,C,D,H; A=(0,0); H=(1,0); B=(2,0); D=(5,0...
human
A whole block of modeling clay is a right rectangular prism six inches by two inches by one inch. How many whole blocks need to be unwrapped to mold a cylindrical sculpture seven inches high and four inches in diameter?
gpt
The cylindrical sculpture has radius two inches and uses $\pi(2^2)(7)=28\pi \approx 87.96$ cubic inches of modeling clay. Each block contains $(6)(2)(1)=12$ cubic inches of modeling clay. If we have 7 blocks, then we have 84 cubic inches of clay which is not enough, so we need $\boxed{8}$ blocks of clay, and we see 9...
human
Isosceles triangle $ABE$ of area 100 square inches is cut by $\overline{CD}$ into an isosceles trapezoid and a smaller isosceles triangle. The area of the trapezoid is 75 square inches. If the altitude of triangle $ABE$ from $A$ is 20 inches, what is the number of inches in the length of $\overline{CD}$? [asy] draw((-...
gpt
The area of triangle $ABE$ is $\frac{1}{2}(\text{base})(\text{height})=\frac{1}{2}(BE)(20\text{ in.})$. Setting this equal to $100$ square inches we find $BE=10$ inches. The area of triangle $ACD$ is $100-75=25$ square inches. Since triangle $ACD$ is similar to triangle $ABE$ and the ratio of their areas is $\frac{1}...
human
A bridge is built by suspending a plank of wood between two triangular wedges with equal heights, as in the following diagram: [asy] import olympiad; import math; // Draw triangles pair A = (0, 1); pair B = (-cos(1.3962), 0); pair C = (cos(1.3962), 0); pair D = (2, 1); pair E = (2-cos(1.3089), 0); pair F = (2+cos(1.30...
gpt
There are several ways to proceed, and here is one. Since $\triangle ABC$ and $\triangle DEF$ are both isosceles, it should be easy to find that $\angle B = \angle C = 80^\circ$ and $\angle E = \angle F = 75^\circ.$ Now, connect $C$ and $E$: [asy] import olympiad; import math; // Draw triangles pair A = (0, 1); pair ...
human
What is the degree measure of angle $LOQ$ when polygon $\allowbreak LMNOPQ$ is a regular hexagon? [asy] draw((-2,0)--(-1,1.73205081)--(1,1.73205081)--(2,0)--(1,-1.73205081)--(-1,-1.73205081)--cycle); draw((-1,-1.73205081)--(1,1.73205081)--(1,-1.73205081)--cycle); label("L",(-1,-1.73205081),SW); label("M",(-2,0),W); lab...
gpt
The sum of the interior angles of an $n$-sided polygon is $180(n-2)$. For a regular hexagon, the interior angles sum to $180(4)$, so each interior angle has a measure of $\frac{180(4)}{6}=30\cdot4=120^\circ$. Since $\overline{PO}$ and $\overline{PQ}$ are congruent sides of a regular hexagon, $\triangle POQ$ is an isosc...
human
The line $y = b-x$ with $0 < b < 4$ intersects the $y$-axis at $P$ and the line $x=4$ at $S$. If the ratio of the area of triangle $QRS$ to the area of triangle $QOP$ is 9:25, what is the value of $b$? Express the answer as a decimal to the nearest tenth. [asy] draw((0,-3)--(0,5.5),Arrows); draw((4,-3.5)--(4,5),Arrows...
gpt
The line $y=b-x$ intersects the $x$-axis at the point where $0 = b-x$, or $x=b$. So, we seek the $x$-coordinate of point $Q$. Since the $y$-axis is parallel to the line $x = 4$, we see that $\angle QSR = \angle QPO$. Also $QOP = QRS = 90$. Thus $\triangle QOP \sim \triangle QRS$, so $\frac{[QRS]}{[QOP]} =\left(\fra...
human
Two vertices of an obtuse triangle are $(6,4)$ and $(0,0)$. The third vertex is located on the negative branch of the $x$-axis. What are the coordinates of the third vertex if the area of the triangle is 30 square units?
gpt
We know that, for a triangle, area = 1/2(base)(height), which equals 30 in this problem. We also know that the height of the triangle is 4 if we use the horizontal leg on the x-axis as the base. Now we can plug this information into the equation to find the length of the base that runs along the x-axis. The equation is...
human
Triangle $ABC$ has vertices at $A(5,8)$, $B(3,-2)$, and $C(6,1)$. The point $D$ with coordinates $(m,n)$ is chosen inside the triangle so that the three small triangles $ABD$, $ACD$ and $BCD$ all have equal areas. What is the value of $10m + n$?
gpt
If $D$ is the centroid of triangle $ABC$, then $ABD$, $ACD$, and $BCD$ would all have equal areas (to see this, remember that the medians of a triangle divide the triangle into 6 equal areas). There is only one point with this property (if we move around $D$, the area of one of the small triangles will increase and wil...
human
In right triangle $DEF$, we have $\angle D = 25^\circ$, $\angle E = 90^\circ$, and $EF = 9$. Find $DE$ to the nearest tenth. You may use a calculator for this problem.
gpt
We start with a diagram: [asy] pair D,EE,F; EE = (0,0); F = (8,0); D = (0,8*Tan(65)); draw(D--EE--F--D); draw(rightanglemark(F,EE,D,18)); label("$E$",EE,SW); label("$F$",F,SE); label("$D$",D,N); label("$9$",F/2,S); [/asy] We seek $DE$, and we have $EF$ and $\angle D$. We can relate these three with the tangent func...
human
Two circles of radius 2 are centered at $(2,0)$ and at $(0,2)$. What is the area of the intersection of the interiors of the two circles? Express your answer in fully expanded form in terms of $\pi$.
gpt
The two circles intersect at $(0,0)$ and $(2,2)$, as shown. [asy] unitsize(1cm); linewidth(1); draw((-2.5,0)--(5,0),Arrow); draw((0,-2.5)--(0,5),Arrow); draw((-2.5,0)--(5,0),linewidth(0.6)); draw((0,-2.5)--(0,5),linewidth(0.6)); label("$x$",(5,0),S); label("$y$",(0,5),E); for (int i=0; i<6; ++i) { draw((-2+i,-0.2)--(-...
human
The measures of the interior angles of a convex hexagon form an increasing arithmetic sequence. How many such sequences are possible if the hexagon is not equiangular and all of the angle degree measures are positive integers less than $150$ degrees?
gpt
The number of degrees in a hexagon is $(6-2) \cdot 180=720$ degrees. Setting the degree of the smallest angle to be $x$, and the increment to be $d$, we get that the sum of all of the degrees is $x+x+d+x+2d+x+3d+x+4d+x+5d=6x+15d=720$. We want $15d$ to be even so that adding it to an even number $6x$ would produce an ev...
human
What is the ratio of the numerical value of the area, in square units, of an equilateral triangle of side length 4 units to the numerical value of its perimeter, in units? Express your answer as a common fraction in simplest radical form.
gpt
The area of this equilateral triangle is $\frac{4^2 \sqrt{3}}{4}$, and the perimeter is $3 \cdot 4 = 12$. Thus, the ratio of area to perimeter is $\frac{\frac{4^2 \sqrt{3}}{4}}{12}=\boxed{\frac{\sqrt{3}}{3}}$.