AMC 12B 2024

Problems, Step-by-Step Hints, and Solutions

2024 AMC 12B Practice Test

Take the complete 2024 AMC 12B as a timed practice test. You'll have 75 minutes to solve all 25 questions under realistic AMC conditions. Submit your test to see your official-style score and review detailed solutions.

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1.
In a long line of people arranged left to right, the 1013th person from the left is also the 1010th person from the right. How many people are in the line?
(A)  2021\text{(A)}\;2021(B)  2022\text{(B)}\;2022(C)  2023\text{(C)}\;2023(D)  2024\text{(D)}\;2024(E)  2025\text{(E)}\;2025
2.
What is 10!−7!⋅6!10!-7!\cdot6!?
(A)  −120\text{(A)}\;-120(B)  0\text{(B)}\;0(C)  120\text{(C)}\;120(D)  600\text{(D)}\;600(E)  720\text{(E)}\;720
3.
For how many integer values of xx is ∣2x∣≤7π|2x|\le7\pi?
(A)  16\text{(A)}\;16(B)  17\text{(B)}\;17(C)  19\text{(C)}\;19(D)  20\text{(D)}\;20(E)  21\text{(E)}\;21
4.
Balls numbered 1,2,3,…1,2,3,\ldots are deposited in 5 bins, labeled AA, BB, CC, DD, and EE, using the following procedure. Ball 1 is deposited in bin AA, and balls 2 and 3 are deposited in bin BB. The next 3 balls are deposited in bin CC, the next 4 in bin DD, and so on, cycling back to bin AA after balls are deposited in bin EE. (For example, balls numbered 22,23,…,2822,23,\ldots,28 are deposited in bin BB at step 7 of this process.) In which bin is ball 2024 deposited?
(A)  A\text{(A)}\;\text{A}(B)  B\text{(B)}\;\text{B}(C)  C\text{(C)}\;\text{C}(D)  D\text{(D)}\;\text{D}(E)  E\text{(E)}\;\text{E}
5.
In the following expression, Melanie changed some of the plus signs to minus signs:
1+3+5+7+⋯+97+991+3+5+7+\cdots+97+99
When the new expression was evaluated, it was negative. What is the least number of plus signs that Melanie could have changed to minus signs?
(A)  14\text{(A)}\;14(B)  15\text{(B)}\;15(C)  16\text{(C)}\;16(D)  17\text{(D)}\;17(E)  18\text{(E)}\;18
6.
The national debt of the United States is on track to reach 5⋅10135\cdot10^{13} dollars by 2033. How many digits does this number of dollars have when written as a numeral in base 5? (The approximation of log⁡105\log_{10}5 as 0.70.7 is sufficient for this problem.)
(A)  18\text{(A)}\;18(B)  20\text{(B)}\;20(C)  22\text{(C)}\;22(D)  24\text{(D)}\;24(E)  26\text{(E)}\;26
7.
In the figure below WXYZWXYZ is a rectangle with WX=4WX=4 and WZ=8WZ=8. Point MM lies on XY‾\overline{XY}, point AA lies on YZ‾\overline{YZ}, and ∠WMA\angle WMA is a right angle. The areas of △WXM\triangle WXM and △WAZ\triangle WAZ are equal. What is the area of △WMA\triangle WMA?
Rectangle WXYZ with WX = 4 and WZ = 8. M lies on XY, A lies on YZ, WM is perpendicular to MA, and WA is drawn.
(A)  13\text{(A)}\;13(B)  14\text{(B)}\;14(C)  15\text{(C)}\;15(D)  16\text{(D)}\;16(E)  17\text{(E)}\;17
8.
What value of xx satisfies (log⁡2x)(log⁡3x)log⁡2x+log⁡3x=2?\frac{(\log_2 x)(\log_3 x)}{\log_2 x+\log_3 x}=2?
(A)  25\text{(A)}\;25(B)  32\text{(B)}\;32(C)  36\text{(C)}\;36(D)  42\text{(D)}\;42(E)  48\text{(E)}\;48
9.
A dartboard is the region BB in the coordinate plane consisting of points (x,y)(x,y) such that ∣x∣+∣y∣≤8|x|+|y|\le 8. A target TT is the region where (x2+y2−25)2≤49(x^2+y^2-25)^2\le 49. A dart is thrown and lands at a random point in BB. The probability that the dart lands in TT can be expressed as mn⋅π\frac{m}{n}\cdot\pi, where mm and nn are relatively prime positive integers. What is m+nm+n?
(A)  39\text{(A)}\;39(B)  71\text{(B)}\;71(C)  73\text{(C)}\;73(D)  75\text{(D)}\;75(E)  135\text{(E)}\;135
10.
A list of 9 real numbers consists of 1,2.2,3.2,5.2,6.2,1, 2.2, 3.2, 5.2, 6.2, and 77, as well as xx, yy, and zz, with x≤y≤zx\le y\le z. The range of the list is 77, and the mean and the median are both positive integers. How many ordered triples (x,y,z)(x,y,z) are possible?
(A)  1\text{(A)}\;1(B)  2\text{(B)}\;2(C)  3\text{(C)}\;3(D)  4\text{(D)}\;4(E)  infinitely many\text{(E)}\;\text{infinitely many}

AMC 12B 2024 (Problem 11)

TrigonometryMedium
11.
Let xn=sin⁡2(n∘)x_n=\sin^2(n^\circ). What is the mean of x1,x2,x3,…,x90x_1,x_2,x_3,\ldots,x_{90}?
(A)  1145\text{(A)}\;\frac{11}{45}(B)  2245\text{(B)}\;\frac{22}{45}(C)  89180\text{(C)}\;\frac{89}{180}(D)  12\text{(D)}\;\frac{1}{2}(E)  91180\text{(E)}\;\frac{91}{180}
12.
Suppose zz is a complex number with positive imaginary part, with real part greater than 11, and with ∣z∣=2|z|=2. In the complex plane, the four points 00, zz, z2z^2, and z3z^3 are the vertices of a quadrilateral with area 1515. What is the imaginary part of zz?
(A)  34\text{(A)}\;\frac{3}{4}(B)  1\text{(B)}\;1(C)  43\text{(C)}\;\frac{4}{3}(D)  32\text{(D)}\;\frac{3}{2}(E)  53\text{(E)}\;\frac{5}{3}
13.
There are real numbers xx, yy, hh, and kk that satisfy the system of equations
x2+y2−6x−8y=hx2+y2−10x+4y=k\begin{aligned}x^2+y^2-6x-8y&=h\\[8pt]x^2+y^2-10x+4y&=k\end{aligned}
What is the minimum possible value of h+kh+k?
(A)  −54\text{(A)}\;-54(B)  −46\text{(B)}\;-46(C)  −34\text{(C)}\;-34(D)  −16\text{(D)}\;-16(E)  16\text{(E)}\;16

Solution 1

Solution 2

14.
How many different remainders can result when the 100100th power of an integer is divided by 125125?
(A)  1\text{(A)}\;1(B)  2\text{(B)}\;2(C)  5\text{(C)}\;5(D)  25\text{(D)}\;25(E)  125\text{(E)}\;125

AMC 12B 2024 (Problem 15)

Coordinate GeometryMedium
15.
A triangle in the coordinate plane has vertices A(log⁡21,log⁡22)A(\log_2 1,\log_2 2), B(log⁡23,log⁡24)B(\log_2 3,\log_2 4), and C(log⁡27,log⁡28)C(\log_2 7,\log_2 8). What is the area of △ABC\triangle ABC?
(A)  log⁡237\text{(A)}\;\log_2\frac{\sqrt{3}}{7}(B)  log⁡237\text{(B)}\;\log_2\frac{3}{\sqrt{7}}(C)  log⁡273\text{(C)}\;\log_2\frac{7}{\sqrt{3}}(D)  log⁡2117\text{(D)}\;\log_2\frac{11}{\sqrt{7}}(E)  log⁡2113\text{(E)}\;\log_2\frac{11}{\sqrt{3}}
16.
A group of 16 people will be partitioned into 4 indistinguishable 4-person committees. Each committee will have one chairperson and one secretary. The number of different ways to make these assignments can be written as 3rM3^rM, where rr and MM are positive integers and MM is not divisible by 3. What is rr?
(A)  5\text{(A)}\;5(B)  6\text{(B)}\;6(C)  7\text{(C)}\;7(D)  8\text{(D)}\;8(E)  9\text{(E)}\;9
17.
Integers aa and bb are randomly chosen without replacement from the set of integers with absolute value not exceeding 1010. What is the probability that the polynomial x3+ax2+bx+6x^3+ax^2+bx+6 has 33 distinct integer roots?
(A)  1240\text{(A)}\;\frac{1}{240}(B)  1221\text{(B)}\;\frac{1}{221}(C)  1105\text{(C)}\;\frac{1}{105}(D)  184\text{(D)}\;\frac{1}{84}(E)  163\text{(E)}\;\frac{1}{63}
18.
The Fibonacci numbers are defined by F1=1F_1=1, F2=1F_2=1, and Fn=Fn−1+Fn−2F_n=F_{n-1}+F_{n-2} for n≥3n\ge3. What is
F2F1+F4F2+F6F3+⋯+F20F10?\frac{F_2}{F_1}+\frac{F_4}{F_2}+\frac{F_6}{F_3}+\cdots+\frac{F_{20}}{F_{10}}?
(A)  318\text{(A)}\;318(B)  319\text{(B)}\;319(C)  320\text{(C)}\;320(D)  321\text{(D)}\;321(E)  322\text{(E)}\;322
19.
Equilateral △ABC\triangle ABC with side length 1414 is rotated about its center by angle θ\theta, where 0<θ<60∘0<\theta<60^\circ, to form △DEF\triangle DEF. See the figure. The area of hexagon ADBECFADBECF is 91391\sqrt3. What is tan⁡θ\tan\theta?
Equilateral triangle ABC and its rotation DEF about their common center, forming hexagon ADBECF.
(A)  34\text{(A)}\;\frac{3}{4}(B)  5311\text{(B)}\;\frac{5\sqrt3}{11}(C)  45\text{(C)}\;\frac{4}{5}(D)  1113\text{(D)}\;\frac{11}{13}(E)  7313\text{(E)}\;\frac{7\sqrt3}{13}
20.
Suppose AA, BB, and CC are points in the plane with AB=40AB=40 and AC=42AC=42, and let xx be the length of the line segment from AA to the midpoint of BC‾\overline{BC}. Define a function ff by letting f(x)f(x) be the area of △ABC\triangle ABC. Then the domain of ff is an open interval (p,q)(p,q), and the maximum value rr of f(x)f(x) occurs at x=sx=s. What is p+q+r+sp+q+r+s?
(A)  909\text{(A)}\;909(B)  910\text{(B)}\;910(C)  911\text{(C)}\;911(D)  912\text{(D)}\;912(E)  913\text{(E)}\;913
21.
The measures of the smallest angles of three different right triangles sum to 90∘90^\circ. All three triangles have side lengths that are primitive Pythagorean triples. Two of them are 3−4−53-4-5 and 5−12−135-12-13. What is the perimeter of the third triangle?
(A)  40\text{(A)}\;40(B)  126\text{(B)}\;126(C)  154\text{(C)}\;154(D)  176\text{(D)}\;176(E)  208\text{(E)}\;208
22.
Let △ABC\triangle ABC be a triangle with integer side lengths such that ∠B=2∠A\angle B=2\angle A. What is the least possible perimeter of such a triangle?
(A)  13\text{(A)}\;13(B)  14\text{(B)}\;14(C)  15\text{(C)}\;15(D)  16\text{(D)}\;16(E)  17\text{(E)}\;17
23.
A right pyramid has regular octagon ABCDEFGHABCDEFGH with side length 11 as its base and apex VV. Segments AV‾\overline{AV} and DV‾\overline{DV} are perpendicular. What is the square of the height of the pyramid?
(A)  1\text{(A)}\;1(B)  1+22\text{(B)}\;\frac{1+\sqrt{2}}{2}(C)  2\text{(C)}\;\sqrt{2}(D)  32\text{(D)}\;\frac{3}{2}(E)  2+23\text{(E)}\;\frac{2+\sqrt{2}}{3}
24.
What is the number of ordered triples (a,b,c)(a,b,c) of positive integers, with a≤b≤c≤9a\le b\le c\le 9, such that there exists a non-degenerate triangle △ABC\triangle ABC with an integer inradius for which aa, bb, and cc are the lengths of the altitudes from AA to BC‾\overline{BC}, BB to AC‾\overline{AC}, and CC to AB‾\overline{AB}, respectively? (Recall that the inradius of a triangle is the radius of the largest possible circle that can be inscribed in the triangle.)
(A)  2\text{(A)}\;2(B)  3\text{(B)}\;3(C)  4\text{(C)}\;4(D)  5\text{(D)}\;5(E)  6\text{(E)}\;6
25.
Pablo will decorate each of 6 identical white balls with either a striped or a dotted pattern, using either red or blue paint. He will decide on the color and pattern for each ball by flipping a fair coin for each of the 12 decisions he must make. After the paint dries, he will place the 6 balls in an urn. Frida will randomly select one ball from the urn and note its color and pattern. The events "the ball Frida selects is red" and "the ball Frida selects is striped" may or may not be independent, depending on the outcome of Pablo's coin flips. The probability that these two events are independent can be written as mn\frac{m}{n}, where mm and nn are relatively prime positive integers. What is mm? (Recall that two events AA and BB are independent if P(A and B)=P(A)⋅P(B)P(A\text{ and }B)=P(A)\cdot P(B).)
(A)  243\text{(A)}\;243(B)  245\text{(B)}\;245(C)  247\text{(C)}\;247(D)  249\text{(D)}\;249(E)  251\text{(E)}\;251