Problem Solving

Hi swerve,

We're told that a set has exactly five CONSECUTIVE positive integers starting with 1. We're asked for the percentage decrease in the average when the greatest number is removed from the set. This question requires the use of the Percent Change Formula:

Percent Change = (New - Old)/(Old) = (Difference)/(Original

The original set of numbers is 1, 2, 3, 4, 5, so the average of that set is (1+2+3+4+5)/5 = 15/5 = 3

Once we remove the greatest number, we're left with 1, 2, 3, 4, so the average of that new set is (1+2+3+4)/4 = 10/4 = 2.5

The Percent Change would be (2.5 - 3)/3 = .5/3 = 1/6 = 16 2/3%

Final Answer: E

GMAT assassins aren't born, they're made,
Rich

swerve wrote:A set has exactly five consecutive positive integers starting with 1. What is the percentage decrease in the average when the greatest number is removed from the set?

A. 5
B. 8.5
C. 12.5
D. 15.2
E. 16.4

What's the source of this question?
It seems very un-GMAT-like to "round" 16 2/3 to 16.4 without some kind of language that suggests we're looking for the best APPROXIMATE answer.

swerve wrote:A set has exactly five consecutive positive integers starting with 1. What is the percentage decrease in the average when the greatest number is removed from the set?

A. 5
B. 8.5
C. 12.5
D. 15.2
E. 16.4

The original average = (1 + 2 + 3 + 4 + 5)/5 = 3.

The new average = (1 + 2 + 3 + 4)/4 = 2.5

(2.5 - 3)/3 x 100 = -0.5/3 x 100 = -1/6 x 100 ≈ -16.7

We see that the average is decreased by approximately 16.7%.

Answer: E

swerve wrote:A set has exactly five consecutive positive integers starting with 1. What is the percentage decrease in the average when the greatest number is removed from the set?

A. 5
B. 8.5
C. 12.5
D. 15.2
E. 16.4

The original average = (1 + 2 + 3 + 4 + 5)/5 = 3.

The new average = (1 + 2 + 3 + 4)/4 = 2.5

(2.5 - 3)/3 x 100 = -0.5/3 x 100 = -1/6 x 100 ≈ -16.7

We see that the average is decreased by approximately 16.7%.

Answer: E