Question

The mean of first 5 observations is 20 and the mean of last 5

observations is 45. What is mean of all 10 observations?​

Answer 1

SOLUTION

GIVEN

The mean of first 5 observations is 20 and the mean of last 5 observations is 45

TO DETERMINE

The mean of the all 10 observations

EVALUATION

Here it is given that mean of first 5 observations is 20 and the mean of last 5 observations is 45

Sum of first 5 observations

= 5 × 20

= 100

Sum of last 5 observations

= 5 × 45

= 225

So total number of observations = 5 + 5 = 10

∴ Sum of 10 observations

= 100 + 225

= 325

Hence the required mean of the all 10 observations

= 325 ÷ 10

= 32.5

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