In calculating the mean of 8 numbers, a boy mistakenly us...
In calculating the mean of 8 numbers, a boy mistakenly used 17 instead of 25 as one of the numbers. If he obtained 20 as the mean, find the correct mean.
24
23
21
19
Correct answer is C
Let the sum of the 8 numbers = y.
y8=20⟹y=20×8=160
160−17=143(the sum of the other 7 numbers)
mean=143+258=1688
= 21
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