GMAT Quantitative Reasoning Practice Test 5

Question : 77 of 100

Marks: +1, -0

5 numbers are randomly chosen. If their average is 20 , how many of the numbers are larger than 15 ?
(1) One of the numbers is 15.
(2) The average of three of the numbers is 15.

Statement (1) BY ITSELF is sufficient to answer the question, but statement (2) by itself is not.
Statement (2) BY ITSELF is sufficient to answer the question, but statement (1) by itself is not.
Statements (1) and (2) TAKEN TOGETHER are sufficient to answer the question, even though NEITHER statement BY ITSELF is sufficient.
Either statement BY ITSELF is sufficient to answer the question.
Statements (1) and (2) TAKEN TOGETHER are NOT sufficient to answer the question, requiring more data pertaining to the problem.

Validate

Solution:

Let's look at two cases, where each one will give out different results.
One of the numbers is 15 and three more are 15,15 and 15 (with an average of 15).
The sum of all the numbers should be

20 × 5=100

.
The sum of the numbers we picked up is

15 × 4=60

and therefore the last number should be 40 which is greater than 15 . The answer in this case is 1 .
Take another case: One of the numbers is 15 and three more are 14, 15 and 16 (with an average of 15 ). In this case there will be 2 numbers over 15 . More data is required.

Go to Question:

Prev Question

Next Question