The average of 18 numbers is 37.5. If six numbers that have an average of x are added to them, the average of all the numbers increases by one. The value of x is:
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 41.5
Sum of the numbers = 37.5 × 18 
Sum of the six numbers = 6 × x = 6x
Average of all numbers = 37.5 + 1 = 38.5
675 + 6x = 24 × 38.5
6x = 924 - 675
6x = 249
⇒ x = 249/6 = 41.5