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AMC 12 2010 B

Question 1

Makarla attended two meetings during her -hour work day. The first meeting took minutes and the second meeting took twice as long. What percent of her work day was spent attending meetings?

Solution

  
  2020-07-09 06:38:34

Question 2

A big is formed as shown. What is its area?

Solution

  
  2020-07-09 06:38:34

Question 3

A ticket to a school play cost dollars, where is a whole number. A group of 9th graders buys tickets costing a total of $, and a group of 10th graders buys tickets costing a total of $. How many values for are possible?

Solution

  
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Question 4

A month with days has the same number of Mondays and Wednesdays. How many of the seven days of the week could be the first day of this month?

Solution

  
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Question 5

Lucky Larry's teacher asked him to substitute numbers for , , , , and in the expression and evaluate the result. Larry ignored the parentheses but added and subtracted correctly and obtained the correct result by coincidence. The numbers Larry substituted for , , , and were , , , and , respectively. What number did Larry substitute for ?

Solution

Simply come up with a linear equation based on what Larry did with e as the only variable, and then solve e.
  
jimmy  2016-10-01 22:01:25

Question 6

At the beginning of the school year, of all students in Mr. Wells' math class answered "Yes" to the question "Do you love math", and answered "No." At the end of the school year, answered "Yes" and answered "No." Altogether, of the students gave a different answer at the beginning and end of the school year. What is the difference between the maximum and the minimum possible values of ?

Solution

  
  2020-07-09 06:38:35

Question 7

Shelby drives her scooter at a speed of miles per hour if it is not raining, and miles per hour if it is raining. Today she drove in the sun in the morning and in the rain in the evening, for a total of miles in minutes. How many minutes did she drive in the rain?

Solution

  
  2020-07-09 06:38:35

Question 8


Every high school in the city of Euclid sent a team of students to a math contest. Each participant in the contest received a different score. Andrea's score was the median among all students, and hers was the highest score on her team. Andrea's teammates Beth and Carla placed th and th, respectively. How many schools are in the city?

Solution

  
  2020-07-09 06:38:35

Question 9

Let be the smallest positive integer such that is divisible by , is a perfect cube, and is a perfect square. What is the number of digits of ?

Solution

  
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Question 10

The average of the numbers and is . What is ?

Solution

  
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Question 11


A palindrome between and is chosen at random. What is the probability that it is divisible by ?

Solution

  
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Question 12

For what value of does

Solution

  
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Question 13

In , and . What is ?

Solution

  
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Question 14

Let , , , , and be positive integers with and let be the largest of the sums , , and . What is the smallest possible value of ?

Solution

Given a constraint, try to max. or min. a variable. You will see this kind of problems quite often in AMC.
Note that to min. M and under the hard constraint of a+b+c+d+e=2010, you will need to

1. make a+b, b+c, c+d, and d+e as small as possible.
2. make a+b, b+c, c+d, and d+e as close as possible.

An intuitive attempt is to divide 2010 by 5, which will give you 402. This will make a+b, b+c, c+d, and d+e very close (actually identical), but it may not be the smallest possible.
We note that b and d are participating in all 4 expressions, so if we re-distribute some of their values to a, c, and e, we can get a better #1 without impacting #2.
We note that (402+402)/3 = 268; but we cannot distribute all of 402+402=804 as we at least must keep b and d to be 1. So we give: a=402+268-1, b=1, c=402+268-1, d=1, and e=402+268.
  
jimmy  2016-10-01 22:01:09

Question 15

For how many ordered triples of nonnegative integers less than are there exactly two distinct elements in the set , where ?

Solution

  
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Question 16

Positive integers , , and are randomly and independently selected with replacement from the set . What is the probability that is divisible by ?

Solution

  
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Question 17

The entries in a array include all the digits from through , arranged so that the entries in every row and column are in increasing order. How many such arrays are there?

Solution

  
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Question 18

A frog makes jumps, each exactly meter long. The directions of the jumps are chosen independently at random. What is the probability that the frog's final position is no more than meter from its starting position?

Solution

  
  2020-07-09 06:38:35

Question 19

A high school basketball game between the Raiders and Wildcats was tied at the end of the first quarter. The number of points scored by the Raiders in each of the four quarters formed an increasing geometric sequence, and the number of points scored by the Wildcats in each of the four quarters formed an increasing arithmetic sequence. At the end of the fourth quarter, the Raiders had won by one point. Neither team scored more than points. What was the total number of points scored by the two teams in the first half?

Solution

  
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Question 20

A geometric sequence has , , and for some real number . For what value of does ?


Solution

  
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Question 21

Let , and let be a polynomial with integer coefficients such that

, and
.

What is the smallest possible value of ?

Solution

  
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Question 22

Let be a cyclic quadrilateral. The side lengths of are distinct integers less than such that . What is the largest possible value of ?

Solution

  
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Question 23

Monic quadratic polynomials and have the property that has zeros at and , and has zeros at and . What is the sum of the minimum values of and ?

Solution

  
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Question 24

The set of real numbers for which

is the union of intervals of the form . What is the sum of the lengths of these intervals?

Solution

  
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Question 25

For every integer , let be the largest power of the largest prime that divides . For example . What is the largest integer such that divides

?


Solution

  
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Answer Keys


Question 1: C
Question 2: A
Question 3: E
Question 4: B
Question 5: D
Question 6: D
Question 7: C
Question 8: B
Question 9: E
Question 10: B
Question 11: E
Question 12: D
Question 13: C
Question 14: B
Question 15: D
Question 16: E
Question 17: D
Question 18: C
Question 19: E
Question 20: E
Question 21: B
Question 22: D
Question 23: A
Question 24: C
Question 25: D