The average of 17 numbers is 10.9. If the average of the first nine is 10.5 and that of the last nine is 11.4, the middle number is:
A
11.8
B
11.4
C
10.9
D
11.7
Correct Option:
A
Explanation
The total of all 17 numbers is 17 × 10.9 = 185.3. The first nine total 94.5 and the last nine total 102.6. The middle number is counted in both groups, so it equals 94.5 + 102.6 − 185.3 = 11.8.
