The mean of a set of 10 numbers is 56. If the mean of the
MATHEMATICS
WAEC 2022
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
Correct Answer: B. 65
Explanation
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
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