The average of 18 numbers is 30. The average of 1st 8 numbers is 17 and the average of the last 8 numbers is 25. What is the average of the 9th and 10th numbers?
A204
B102
C67
D52
Answer:
B. 102
Read Explanation:
The sum of 18 numbers is (18 × 30) = 540
The sum of 1st 8 numbers is ( 17 × 8) = 136
The Sum of the last 8 numbers is ( 25 × 8) = 200
9th number + 10th number = Sum of 18 numbers - (sum of 1st 8 numbers + Sum of last 8 numbers)
= 540 - ( 136 + 200)
= 540 - 336
= 204
The average of the 9th and the 10th number = 204 / 2
= 102