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AMC 12 2004 A

Question 1

Alicia earns dollars per hour, of which is deducted to pay local taxes. How many cents per hour of Alicia's wages are used to pay local taxes?

Solution

  
  2020-07-09 06:38:48

Question 2

On the AMC 12, each correct answer is worth points, each incorrect answer is worth points, and each problem left unanswered is worth points. If Charlyn leaves of the problems unanswered, how many of the remaining problems must she answer correctly in order to score at least ?

Solution

  
  2020-07-09 06:38:49

Question 3

For how many ordered pairs of positive integers is ?

Solution

  
  2020-07-09 06:38:49

Question 4

Bertha has daughters and no sons. Some of her daughters have daughters, and the rest have none. Bertha has a total of daughters and granddaughters, and no great-granddaughters. How many of Bertha's daughters and grand-daughters have no children?

Solution

  
  2020-07-09 06:38:49

Question 5

The graph of the line is shown. Which of the following is true?

Solution

  
  2020-07-09 06:38:49

Question 6

Let , , , , and . Which of the following is the largest?

Solution

  
  2020-07-09 06:38:49

Question 7

A game is played with tokens according to the following rules. In each round, the player with the most tokens gives one token to each of the other players and also places one token into a discard pile. The game ends when some player runs out of tokens. Players , and start with , and tokens, respectively. How many rounds will there be in the game?

Solution

  
  2020-07-09 06:38:49

Question 8

In the overlapping triangles and sharing common side , and are right angles, , , , and and intersect at . What is the difference between the areas of and ?

Solution

  
  2020-07-09 06:38:49

Question 9

A company sells peanut butter in cylindrical jars. Marketing research suggests that using wider jars would increase sales. If the diameter of the jars is increased by without altering the volume, by what percent must the height be decreased?

Solution

  
  2020-07-09 06:38:49

Question 10


The sum of consecutive integers is . What is their median?

Solution

  
  2020-07-09 06:38:49

Question 11


The average value of all the pennies, nickels, dimes, and quarters in Paula's purse is cents. If she had one more quarter, the average value would be cents. How many dimes does she have in her purse?

Solution

  
  2020-07-09 06:38:49

Question 12


Let and . Points and are on the line , and and intersect at . What is the length of ?

Solution

  
  2020-07-09 06:38:49

Question 13


Let be the set of points in the coordinate plane, where each of and may be , , or . How many distinct lines pass through at least two members of ?

Solution

This question is actually very simple: first, draw all the 9 points with the given (a,b) values:

0,0
0,1
0,-1
1,0
1,-1
1,1
-1,0
-1,1
-1,-1

Then try to connect any 2 of these points, and then count the number of lines you have.
  
allenx123456  2016-12-20 19:27:45

Question 14


A sequence of three real numbers forms an arithmetic progression with a first term of . If is added to the second term and is added to the third term, the three resulting numbers form a geometric progression. What is the smallest possible value for the third term in the geometric progression?

Solution

  
  2020-07-09 06:38:49

Question 15


Brenda and Sally run in opposite directions on a circular track, starting at diametrically opposite points. They first meet after Brenda has run meters. They next meet after Sally has run meters past their first meeting point. Each girl runs at a constant speed. What is the length of the track in meters?

Solution

  
  2020-07-09 06:38:49

Question 16


The set of all real numbers for which

is defined is . What is the value of ?

Solution

  
  2020-07-09 06:38:49

Question 17


Let be a function with the following properties:

, and

, for any positive integer .

What is the value of ?

Solution

  
  2020-07-09 06:38:49

Question 18


Square has side length . A semicircle with diameter is constructed inside the square, and the tangent to the semicircle from intersects side at . What is the length of ?


Solution

  
  2020-07-09 06:38:49

Question 19


Circles and are externally tangent to each other, and internally tangent to circle . Circles and are congruent. Circle has radius and passes through the center of . What is the radius of circle ?

Solution

  
  2020-07-09 06:38:49

Question 20


Select numbers and between and independently and at random, and let be their sum. Let and be the results when and , respectively, are rounded to the nearest integer. What is the probability that ?

Solution

Since a, b, and c are between 0 and 1, when we round them, we can only get integers 0 or 1. Therefore, we will have 4 scenarios:

1. 0+0=0
2. 0+1=1
3. 1+0=1
4. 1+1=2

In scenario 1: the prob. for a and b to be rounded to 0 is 1/2 * 1/2 = 1/4. And when a and b are both <0.5, 50% of the times, their sum is smaller than 0.5, which will round to 0. Therefore, the prob. for a and b to be rounded to 0, and c to 0 is 1/4 * 1/2 = 1/8.

In scenario 2: the prob. for a to be rounded to 0 and for b to be rounded to 1 is 1/2 * 1/2 = 1/4; since a = 0.5, their result c is always rounded to 1. Therefore, prob. for scenario 2 is 1/4.

In scenario 3: same as scenario 2. So prob. is 1/4.

In scenario 4: the prob. for a and b to be rounded to 1 is 1/2 * 1/2 = 1/4. And when a and b are both > 0.50, 50% of the times, their sum is smaller than 1.5, which will round to 1. Therefore, the probability for a, b to be rounded to 1, and c to be rounded to 2 is 1/4 * 1/2 = 1/8.

Put them all together: 1/8 + 1/4 + 1/4 + 1/8 = 3/4
  
jimmy  2016-09-16 15:03:35

Question 21


If , what is the value of ?

Solution

  
  2020-07-09 06:38:49

Question 22


Three mutually tangent spheres of radius rest on a horizontal plane. A sphere of radius rests on them. What is the distance from the plane to the top of the larger sphere?

Solution

  
  2020-07-09 06:38:49

Question 23


A polynomial

has real coefficients with and distinct complex zeroes , with and real, , and

Which of the following quantities can be a nonzero number?

Solution

  
  2020-07-09 06:38:49

Question 24

A plane contains points and with . Let be the union of all disks of radius in the plane that cover . What is the area of ?

Solution

  
  2020-07-09 06:38:49

Question 25


For each integer , let denote the base- number . The product can be expressed as , where and are positive integers and is as small as possible. What is the value of ?

Solution

  
  2020-07-09 06:38:49

Answer Keys


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