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AMC 12 2019 A

Question 1

The area of a pizza with radius is percent larger than the area of a pizza with radius inches. What is the integer closest to ?

Solution

  
  2020-07-09 06:39:03

Question 2

Suppose is of . What percent of is ?

Solution

  
  2020-07-09 06:39:03

Question 3

A box contains red balls, green balls, yellow balls, blue balls, white balls, and black balls. What is the minimum number of balls that must be drawn from the box without replacement to guarantee that at least balls of a single color will be drawn?

Solution

  
  2020-07-09 06:39:03

Question 4

What is the greatest number of consecutive integers whose sum is ?

Solution

  
  2020-07-09 06:39:03

Question 5

Two lines with slopes and intersect at . What is the area of the triangle enclosed by these two lines and the line ?

Solution

  
  2020-07-09 06:39:03

Question 6

The figure below shows line with a regular, infinite, recurring pattern of squares and line segments.

How many of the following four kinds of rigid motion transformations of the plane in which this figure is drawn, other than the identity transformation, will transform this figure into itself?

  • some rotation around a point of line
  • some translation in the direction parallel to line
  • the reflection across line
  • some reflection across a line perpendicular to line

Solution

  
  2020-07-09 06:39:03

Question 7

Melanie computes the mean , the median , and the modes of the values that are the dates in the months of . Thus her data consist of , , . . . , , , , and . Let be the median of the modes. Which of the following statements is true?

Solution

  
  2020-07-09 06:39:03

Question 8

For a set of four distinct lines in a plane, there are exactly distinct points that lie on two or more of the lines. What is the sum of all possible values of ?

Solution

  
  2020-07-09 06:39:03

Question 9

A sequence of numbers is defined recursively by , , and for all . Then can be written as , where and are relatively prime positive integers. What is

Solution

  
  2020-07-09 06:39:03

Question 10

The figure below shows circles of radius within a larger circle. All the intersections occur at points of tangency. What is the area of the region, shaded in the figure, inside the larger circle but outside all the circles of radius ?

Solution

  
  2020-07-09 06:39:03

Question 11

For some positive integer , the repeating base- representation of the (base-ten) fraction is . What is ?

Solution

  
  2020-07-09 06:39:03

Question 12

Positive real numbers and satisfy and . What is ?

Solution

  
  2020-07-09 06:39:03

Question 13

How many ways are there to paint each of the integers either red, green, or blue so that each number has a different color from each of its proper divisors?

Solution

  
  2020-07-09 06:39:03

Question 14

For a certain complex number , the polynomial has exactly 4 distinct roots. What is ?

Solution

  
  2020-07-09 06:39:03

Question 15

Positive real numbers and have the property that

and all four terms on the left are positive integers, where denotes the base- logarithm. What is ?

Solution

  
  2020-07-09 06:39:03

Question 16

The numbers are randomly placed into the squares of a grid. Each square gets one number, and each of the numbers is used once. What is the probability that the sum of the numbers in each row and each column is odd?

Solution

  
  2020-07-09 06:39:03

Question 17

Let denote the sum of the th powers of the roots of the polynomial . In particular, , , and . Let , , and be real numbers such that for , , What is ?

Solution

  
  2020-07-09 06:39:03

Question 18

A sphere with center has radius . A triangle with sides of length and is situated in space so that each of its sides is tangent to the sphere. What is the distance between and the plane determined by the triangle?

Solution

  
  2020-07-09 06:39:03

Question 19

In with integer side lengths, What is the least possible perimeter for ?

Solution

  
  2020-07-09 06:39:03

Question 20

Real numbers between and , inclusive, are chosen in the following manner. A fair coin is flipped. If it lands heads, then it is flipped again and the chosen number is if the second flip is heads and if the second flip is tails. On the other hand, if the first coin flip is tails, then the number is chosen uniformly at random from the closed interval . Two random numbers and are chosen independently in this manner. What is the probability that ?

Solution

  
  2020-07-09 06:39:03

Question 21

Let What is

Solution

  
  2020-07-09 06:39:03

Question 22

Circles and , both centered at , have radii and , respectively. Equilateral triangle , whose interior lies in the interior of but in the exterior of , has vertex on , and the line containing side is tangent to . Segments and intersect at , and . Then can be written in the form for positive integers , , , with . What is ?

Solution

  
  2020-07-09 06:39:03

Question 23

Define binary operations and by for all real numbers and for which these expressions are defined. The sequence is defined recursively by and for all integers . To the nearest integer, what is ?

Solution

  
  2020-07-09 06:39:03

Question 24

For how many integers between and , inclusive, is an integer? (Recall that .)

Solution

  
  2020-07-09 06:39:03

Question 25

Let be a triangle whose angle measures are exactly , , and . For each positive integer define to be the foot of the altitude from to line . Likewise, define to be the foot of the altitude from to line , and to be the foot of the altitude from to line . What is the least positive integer for which is obtuse?

Solution

  
  2020-07-09 06:39:03

Answer Keys


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