Mini mock 3
15 problems matching a real contest's position mix, 45 minutes
- 1.2012 AMC 10A #4
Let and . What is the smallest possible degree measure for angle ?
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- 2.2022 AMC 10B #4
A donkey suffers an attack of hiccups and the first hiccup happens at one afternoon. Suppose that the donkey hiccups regularly every seconds. At what time does the donkey’s th hiccup occur?
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- 3.2017 AMC 10A #4
Mia is “helping” her mom pick up toys that are strewn on the floor. Mia’s mom manages to put toys into the toy box every seconds, but each time immediately after those seconds have elapsed, Mia takes toys out of the box. How much time, in minutes, will it take Mia and her mom to put all toys into the box for the first time?
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- 4.2012 AMC 10B #5
Anna enjoys dinner at a restaurant in Washington, D.C., where the sales tax on meals is 10%. She leaves a 15% tip on the price of her meal before the sales tax is added, and the tax is calculated on the pre-tip amount. She spends a total of 27.50 dollars for dinner. What is the cost of her dinner without tax or tip in dollars?
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- 5.2025 AMC 10B #5
In , , , and Let be the center of the circle containing , , and What is the degree measure of ?
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- 6.2024 AMC 10A #7
The product of three integers is . What is the least possible positive sum of the three integers?
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- 7.2015 AMC 10B #13
The line forms a triangle with the coordinate axes. What is the sum of the lengths of the altitudes of this triangle?
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- 8.2021 AMC Fall 10A #13
Each of balls is randomly and independently painted either black or white with equal probability. What is the probability that every ball is different in color from more than half of the other balls?
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- 9.2014 AMC 10B #14
Danica drove her new car on a trip for a whole number of hours, averaging miles per hour. At the beginning of the trip, miles was displayed on the odometer, where is a 3-digit number with and . At the end of the trip, the odometer showed miles. What is ?
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- 10.2018 AMC 10B #17
In rectangle , and . Points and lie on , points and lie on , points and lie on , and points and lie on so that and the convex octagon is equilateral. The length of a side of this octagon can be expressed in the form , where , , and are integers and is not divisible by the square of any prime. What is ?
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- 11.2024 AMC 10A #18
There are exactly positive integers such that the base- integer is divisible by (where is in base ten). What is the sum of the digits of ?
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- 12.2013 AMC 10B #19
The real numbers form an arithmetic sequence with . The quadratic has exactly one root. What is this root?
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- 13.2021 AMC Fall 10B #20
In a particular game, each of players rolls a standard -sided die. The winner is the player who rolls the highest number. If there is a tie for the highest roll, those involved in the tie will roll again and this process will continue until one player wins. Hugo is one of the players in this game. What is the probability that Hugo's first roll was a given that he won the game?
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- 14.2021 AMC Fall 10A #23
For each positive integer , let be twice the number of positive integer divisors of , and for , let . For how many values of is
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- 15.2023 AMC 10B #23
An arithmetic sequence of positive integers has terms, initial term , and common difference . Carl wrote down all the terms in this sequence correctly except for one term, which was off by . The sum of the terms he wrote down was . What is ?
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Answers
| # | Answer | Topic and the idea it turns on |
|---|---|---|
| 1 | C | Angles & Polygons — Rays BC and BD can lie on the same side of ray BA or on opposite sides; the same side gives 24 - 20 = 4, the smaller option. |
| 2 | A | Clocks, Calendars & Time — The 700th hiccup is 699 gaps after the first, so it occurs 699 × 5 = 3495 seconds, i.e. 58 minutes 15 seconds, after 4:00. |
| 3 | B | Games & Processes — Each 30-second cycle nets one toy, but the box reaches 30 the instant Mom drops in her third batch, before Mia can react, so 27 cycles plus one more deposit. |
| 4 | D | Ratios, Percents & Averages — Tax and tip are both percentages of the same base price, so the total is 1.25 times the meal: 27.50 / 1.25 = 22. |
| 5 | C | Circles — Angle B is obtuse, so it subtends the major arc: the central angle AOC is 360 - 260 = 100 degrees, and OA = OC gives 40. |
| 6 | B | Divisibility & Factors — Allow two negative factors: (−1)(−6)(10) = 60 has sum 3, and checking the factor triples shows a positive sum of 1 or 2 is impossible. |
| 7 | E | Triangles: Area & Pythagorean — The intercepts give a 5-12-13 right triangle; two altitudes are the legs, and the third is (leg times leg)/hypotenuse = 60/13. |
| 8 | D | Basic Probability — A black ball needs at least 3 white balls and a white ball needs at least 3 black, so the split must be exactly 3-3: C(6,3)/2^6 = 20/64. |
| 9 | D | Bases & Digits — Reversing a 3-digit number changes it by 99(c - a); equating with 55h forces c - a to be a multiple of 5, so (a, c) = (1, 6). |
| 10 | B | Triangles: Area & Pythagorean — With side s, the corner legs are (8-s)/2 and (6-s)/2, and the Pythagorean theorem gives s^2 + 14s - 50 = 0, so s = -7 + 3 sqrt(11). |
| 11 | D | Bases & Digits — Because 2024_b = 2(b³+b+2), the condition is b³+b+2 ≡ 0 (mod 8), which holds exactly when b ≡ 3, 6, 7 (mod 8). |
| 12 | D | Quadratics — One root means b^2 = 4ac with b = (a+c)/2; dividing by a^2 gives a quadratic in t = c/a, and the root is -b/(2a) = -(1+t)/4. |
| 13 | C | Conditional Probability & States — P(Hugo wins) is 1/4 by symmetry, and given a first roll of 5 he wins with probability sum over k other 5s of C(3,k)(1/6)^k(4/6)^(3-k)/(k+1). |
| 14 | D | Divisibility & Factors — Since f_1(n) = 2d(n) <= 20 here, iterating small even numbers shows only 12, 18, 20 reach 12; so count n <= 50 with d(n) in {6, 9, 10}. |
| 15 | B | Sequences & Series — The true sum is 221 or 223, so n divides 442 or 446; d >= 2 forces n <= 14, leaving n = 13, d = 2, a = 5. |