In computing the mean of 8 numbers, a boy mistakenly used 17 instead of 25
FURTHER MATHEMATICS
WAEC 2012
In computing the mean of 8 numbers, a boy mistakenly used 17 instead of 25 as one of the numbers and obtained 20 as the mean. Find the correct mean
- A. 19
- B. 21
- C. 23
- D. 24
Correct Answer: B. 21
Explanation
\(Mean = \frac{sum of items}{total number of items}\)
\(20 = \frac{x}{8} \implies x = 160\)
The sum of the 7 nos = 160 - 17 = 143
Correct mean = \(\frac{143 + 25}{8} = \frac{168}{8} = 21\)
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