The average of 25 numbers is 55 . The average of first 11 numbers is 51 and the average of last 10 numbers is 56 . What is the average of 66,70 and the remaining 4 numbers out of given 25 numbers?

Correct option is B

Given:

- Total 25 numbers, average = 55 
- First 11 numbers, average = 51 
- Last 10 numbers, average = 56 
- Two numbers out of middle 6 are 66 and 70
Solution:

Total sum of 25 numbers = 25 × 55 = 1375
Sum of first 11 numbers = 11 × 51 = 561
Sum of last 10 numbers = 10 × 56 = 560
Sum of middle 4 numbers = 1375 -  (561 + 560) = 254
Two numbers are 66 and 70 => Sum = 66 + 70 = 136
Sum of 66, 74 and Remaining 4 numbers' sum = 254 + 136 = 390
Average of all 6 numbers  ​= $$\frac{390}{6}$$ = 65​