Question

The mean of 21 numbers is 15. If each number is multiplied by 2, what will be the new mean and hence state the relation between the new mean and the old mean.

Answer 1

Mean of 21 numbers is 15.

If each number, is multiplied by 2, then the new mean is also twice the old mean.

So, New Mean = 2 * Old Mean = 2 * 15 = 30

Thus, whatever arithmetical operations are done to each number, the same operations are to be done on the old mean to find the new mean.

Answer 2

15 = sum of old observations / 21

15*21 = 315 = sum of old observations

2 * sum of old observations = 315 * 2 = 630

Mean = sum of obsv.s / no. of obsv

= 630 / 21 = 30

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