The mean of a set of 10 numbers is 56. If the mean of the first nine numbers is 55, find the 10th number.
A
75
B
65
C
55
D
45
Verified Correct Answer: B.
Step-by-Step Mathematical Solution
10th number must be over 56 (as it increases the average)
55 x 9 = 495 = sum of first 9 numbers
56 x 10 = 560 = sum of all 10 numbers
560 - 495 = 65 = 10th number
Source: WAEC / JAMB / NECO Classroom Archive (Record #64844)