WAEC - Further Mathematics (2012 - No. 23)
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
19
21
23
24
Explicació
\(Mean = \frac{sum of items}{total number of items}\)
\(20 = \frac{x}{8} \implies x = 160\)
The sum of the 7 nos = 160 - 17 = 143
Correct mean = \(\frac{143 + 25}{8} = \frac{168}{8} = 21\)