Question

in a class test, the mean marks scored by a class of 40 students was calculated as 18.2. later on, it was detected that the marks of one student was wrongly copied as 21 instead of 29. Find the correct mean

Answer 1

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Answer 2

The correct mean is 18.4

Step-by-step explanation:

$Average = \frac{\text{Sum of all observations}}{\text{No. of observations}}$

We are given that in a class test, the mean marks scored by a class of 40 students was calculated as 18.2.

So, $18.2=\frac{\text{Sum of scores of 40 students}}{40}\\18.2 \times 40 = \text{Sum of scores of 40 students}\\728 = \text{Sum of scores of 40 students}$

It was detected that the marks of one student was wrongly copied as 21 instead of 29

New sum = 728 - 21+29=736

New average =$\frac{736}{40}=18.4$

Hence The correct mean is 18.4

#Learn more:

Mean of 50 observations is 80.4 but 96 was misread as 69 find the correct mean

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