Difference between revisions of "2021 AMC 10A Problems"
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==Problem 6== | ==Problem 6== | ||
+ | Chantal and Jean start hiking from a trailhead toward a fire tower. Jean is wearing a heavy backpack and walks slower. Chantal starts walking at <math>4</math> miles per hour. Halfway to the tower, the trail becomes really steep, and Chantal slows down to <math>2</math> miles per hour. After reaching the tower, she immediately turns around and descends the steep part of the trail at <math>3</math> miles per hour. She meets Jean at the halfway point. What was Jean's average speed, in miles per hour, until they meet? | ||
+ | |||
+ | <math>\textbf{(A)} ~\frac{12}{13} \qquad\textbf{(B)} ~1 \qquad\textbf{(C)} ~\frac{13}{12} \qquad\textbf{(D)} | ||
+ | ~\frac{24}{13} \qquad\textbf{(E)} ~2</math> | ||
+ | |||
+ | [[2021 AMC 10A Problems/Problem 6|Solution]] | ||
==Problem 7== | ==Problem 7== | ||
+ | Tom has a collection of <math>13</math> snakes, <math>4</math> of which are purple and <math>5</math> of which are happy. He knows that: | ||
+ | All of his happy snakes can add | ||
+ | None of his purple snakes can subtract | ||
+ | All of his snakes that can't subtract also can't add | ||
+ | |||
+ | Which of these conclusions can be drawn about Tom's snakes? | ||
+ | |||
+ | <math>\textbf{(A)}</math> Purple snakes can add. | ||
+ | <math>\textbf{(B)}</math> Purple snakes are happy. | ||
+ | <math>\textbf{(C)}</math> Snakes that can add are purple. | ||
+ | <math>\textbf{(D)}</math> Happy snakes are not purple. | ||
+ | <math>\textbf{(E)}</math> Happy snakes can't subtract. | ||
+ | |||
+ | [[2021 AMC 10A Problems/Problem 7|Solution]] | ||
==Problem 8== | ==Problem 8== | ||
+ | When a student multiplied the number <math>66</math> by the repeating decimal | ||
+ | <cmath>\underline{1}.\underline{a} \underline{b} \underline{a} \underline{b} \cdots = | ||
+ | \underline{1}.\overline{\underline{ab}}</cmath>Where <math>a</math> and <math>b</math> are digits. He did not notice the notation and just multiplied <math>66</math> times <math>\underline{1}.\underline{a}\underline{b}</math>. Later he found that his answer is <math>0.5</math> less than the correct answer. What is the <math>2</math>-digit integer <math>\underline{ab}</math>? | ||
+ | |||
+ | <math>\textbf{(A)} ~15\qquad\textbf{(B)} ~30\qquad\textbf{(C)} ~45\qquad\textbf{(D)} ~60\qquad\textbf{(E)} ~75</math> | ||
+ | |||
+ | [[2021 AMC 10A Problems/Problem 8|Solution]] | ||
==Problem 9== | ==Problem 9== | ||
==Problem 10== | ==Problem 10== |
Revision as of 14:55, 11 February 2021
2021 AMC 10A (Answer Key) Printable versions: • AoPS Resources • PDF | ||
Instructions
| ||
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 |
February 4, 2021, is when the AMC 10A starts.
Contents
- 1 Problem 1
- 2 Problem 2
- 3 Problem 3
- 4 Problem 4
- 5 Problem 5
- 6 Problem 6
- 7 Problem 7
- 8 Problem 8
- 9 Problem 9
- 10 Problem 10
- 11 Problem 11
- 12 Problem 12
- 13 Problem 13
- 14 Problem 14
- 15 Problem 15
- 16 Problem 16
- 17 Problem 17
- 18 Problem 18
- 19 Problem 19
- 20 Problem 20
- 21 Problem 21
- 22 Problem 22
- 23 Problem 23
- 24 Problem 24
- 25 Problem 25
Problem 1
What is the value of
Problem 2
Portia's high school has times as many students as Lara's high school. The two high schools have a total of
students. How many students does Portia's high school have?
Problem 3
The sum of two natural numbers is . One of the two numbers is divisible by
. If the units digit of that number is erased, the other number is obtained. What is the difference of these two numbers?
Problem 4
A cart rolls down a hill, travelling inches the first second and accelerating so that during each successive
-second time interval, it travels
inches more than during the previous
-second interval. The cart takes
seconds to reach the bottom of the hill. How far, in inches, does it travel?
Problem 5
The quiz scores of a class with students have a mean of
. The mean of a collection of
of these quiz scores is
. What is the mean of the remaining quiz scores of terms of
?
Problem 6
Chantal and Jean start hiking from a trailhead toward a fire tower. Jean is wearing a heavy backpack and walks slower. Chantal starts walking at miles per hour. Halfway to the tower, the trail becomes really steep, and Chantal slows down to
miles per hour. After reaching the tower, she immediately turns around and descends the steep part of the trail at
miles per hour. She meets Jean at the halfway point. What was Jean's average speed, in miles per hour, until they meet?
Problem 7
Tom has a collection of snakes,
of which are purple and
of which are happy. He knows that:
All of his happy snakes can add
None of his purple snakes can subtract
All of his snakes that can't subtract also can't add
Which of these conclusions can be drawn about Tom's snakes?
Purple snakes can add.
Purple snakes are happy.
Snakes that can add are purple.
Happy snakes are not purple.
Happy snakes can't subtract.
Problem 8
When a student multiplied the number by the repeating decimal
Where
and
are digits. He did not notice the notation and just multiplied
times
. Later he found that his answer is
less than the correct answer. What is the
-digit integer
?