 # RS Aggarwal Solutions Class 9 Mathematics Solutions for Mean Median And Mode Of Ungrouped Data Exercise 18A in Chapter 18 - Mean Median And Mode Of Ungrouped Data

Question 14 Mean Median And Mode Of Ungrouped Data Exercise 18A

The average height of 30 boys was calculated to be 150cm. It was detected later that one value of 165cm

was wrongly copied as 135cm for the computation of the mean. Find the correct mean.

It is given that

Mean height of 30 boys = 150cm

So the total height = 150 (30) = 4500cm

We know that

Correct sum = 4500 – incorrect value + correct value

By substituting the values

Correct sum = 4500 – 135 + 165 = 4350

So we get

Correct mean = Correct sum/30

By substituting the values

Correct mean = 4530/30 = 151 cm

Therefore, the correct mean is 151 cm.

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