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AMC 12 2005 B

Question 1

A scout troop buys candy bars at a price of five for dollars. They sell all the candy bars at the price of two for dollar. What was their profit, in dollars?

Solution

  
  2020-07-09 06:38:47

Question 2

A positive number has the property that of is . What is ?

Solution

  
  2020-07-09 06:38:47

Question 3

Brianna is using part of the money she earned on her weekend job to buy several equally-priced CDs. She used one ???fth of her money to buy one third of the CDs. What fraction of her money will she have left after she buys all the CDs?

Solution

  
  2020-07-09 06:38:47

Question 4

At the beginning of the school year, Lisa's goal was to earn an A on at least of her quizzes for the year. She earned an A on of the first quizzes. If she is to achieve her goal, on at most how many of the remaining quizzes can she earn a grade lower than an A?

Solution

  
  2020-07-09 06:38:47

Question 5

An -foot by -foot floor is tiled with square tiles of size foot by foot. Each tile has a pattern consisting of four white quarter circles of radius foot centered at each corner of the tile. The remaining portion of the tile is shaded. How many square feet of the floor are shaded?

Solution

  
  2020-07-09 06:38:47

Question 6

In , we have and . Suppose that is a point on line such that lies between and and . What is ?

Solution

  
  2020-07-09 06:38:47

Question 7

What is the area enclosed by the graph of ?

Solution

  
  2020-07-09 06:38:47

Question 8

For how many values of is it true that the line passes through the vertex of the parabola  ?

Solution

  
  2020-07-09 06:38:47

Question 9

On a certain math exam, of the students got points, got points, got points, got points, and the rest got points. What is the difference between the mean and the median score on this exam?

Solution

  
  2020-07-09 06:38:47

Question 10

The first term of a sequence is . Each succeeding term is the sum of the cubes of the digits of the previous terms. What is the term of the sequence?

Solution

The pattern of the number sequence is: 2005, 133, 55, 250, 133, 55, 250, ...
Excluding the 1st number in the sequence, the 2005th number will be the 2004th. 2004 divided by 3 will have a remainder of 0.
Therefore, 2005th number is 250.
  
jimmy  2016-10-01 22:23:04

Question 11

An envelope contains eight bills: ones, fives, tens, and twenties. Two bills are drawn at random without replacement. What is the probability that their sum is $ or more?

Solution

  
  2020-07-09 06:38:47

Question 12

The quadratic equation has roots twice those of , and none of and is zero. What is the value of ?

Solution

  
  2020-07-09 06:38:48

Question 13

Suppose that , , , ... , . What is ?

Solution

  
  2020-07-09 06:38:48

Question 14

A circle having center , with ,is tangent to the lines , and . What is the radius of this circle?

Solution

  
  2020-07-09 06:38:48

Question 15

The sum of four two-digit numbers is . None of the eight digits is and no two of them are the same. Which of the following is not included among the eight digits?

Solution

  
  2020-07-09 06:38:48

Question 16

Eight spheres of radius 1, one per octant, are each tangent to the coordinate planes. What is the radius of the smallest sphere, centered at the origin, that contains these eight spheres?

Solution

  
  2020-07-09 06:38:48

Question 17

How many distinct four-tuples of rational numbers are there with

?

Solution

  
  2020-07-09 06:38:48

Question 18

Let and be points in the plane. Define as the region in the first quadrant consisting of those points such that is an acute triangle. What is the closest integer to the area of the region ?

Solution

  
  2020-07-09 06:38:48

Question 19

Let and be two-digit integers such that is obtained by reversing the digits of . The integers and satisfy for some positive integer . What is ?

Solution

  
  2020-07-09 06:38:48

Question 20

Let and be distinct elements in the set

What is the minimum possible value of

Solution

  
  2020-07-09 06:38:48

Question 21

A positive integer has divisors and has divisors. What is the greatest integer such that divides ?

Solution

  
  2020-07-09 06:38:48

Question 22

A sequence of complex numbers is defined by the rule

where is the complex conjugate of and . Suppose that and . How many possible values are there for ?

Solution

  
  2020-07-09 06:38:48

Question 23

Let be the set of ordered triples of real numbers for which

There are real numbers and such that for all ordered triples in we have What is the value of

Solution

  
  2020-07-09 06:38:48

Question 24

All three vertices of an equilateral triangle are on the parabola , and one of its sides has a slope of . The -coordinates of the three vertices have a sum of , where and are relatively prime positive integers. What is the value of ?

Solution

  
  2020-07-09 06:38:48

Question 25

Six ants simultaneously stand on the six vertices of a regular octahedron, with each ant at a different vertex. Simultaneously and independently, each ant moves from its vertex to one of the four adjacent vertices, each with equal probability. What is the probability that no two ants arrive at the same vertex?

Solution

  
  2020-07-09 06:38:48

Answer Keys


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