kohliankur wrote:
If the average (arithmetic mean) of six different numbers is 25, how many of the numbers are greater than 25?
(1) None of the six numbers is greater than 50.
(2) Three of the six numbers are 7, 8, and 9, respectively.
I have a question , if the problem statement states that there are six distinct number as in this question, shall we consider positive numbers only or negative numbers too?
A number can be any real number - positive integer, negative integer, decimal etc
GMAT often uses the terminology of integers to be more specific "positive integer", "non negative integer", "negative integer" etc.
Anyway, negative integers don't really have any role to play in this question.
Statement 1: None of the six numbers is greater than 50.
It is possible that only 1 number is greater than 25 e.g. 20, 21, 22, 23, 24, 40
It is possible that only 2 numbers are greater than 25 e.g. 21, 22, 23, 24, 29, 31
etc
Not sufficient
Statement 2: Three of the six numbers are 7, 8, and 9, respectively.
It is possible that only 1 number is greater than 25 e.g. 7, 8, 9, 24, 25, 75
It is possible that only 2 numbers are greater than 25 e.g. 7, 8, 9, 25, 41, 60
etc
Not sufficient
Both together, 7, 8 and 9 are 18, 17 and 16 less than 25 respectively. To get the average of 25, the other 3 numbers should together make up this deficit of 18+17+16 = 51.
Since no number can be greater than 50, any one number can make up the deficit of at most 25. To make up the deficit of 51, we need at least 3 numbers. Hence, we can say that 3 numbers will be greater than 25.
Answer (C)