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The mean of 21 observations is 42. If out of 21 given observations, the mean of the first 11 observations is 50 and the mean of the last 11 observatio
Question

The mean of 21 observations is 42. If out of 21 given observations, the mean of the first 11 observations is 50 and the mean of the last 11 observations is 35, then the 11™ observation will be:

A.

53

B.

40

C.

35

D.

50

Correct option is A

Given:

The mean of 21 observations is 42.

The mean of the first 11 observations is 50 .

The mean of the last 11 observations is 35.

Formula Used:

Mean = sum ofall datanumber of data\frac{sum\ of all\ data }{number\ of\ data } 

Solution:

Total of 21 observation = 42 × 21= 882

Total of 1st 11 observation = 11 × 50= 550

Total of last 11 observation = 11 × 35=385

Total  of first and last 11 observation =550+385  935

So, 11th observation = 935 - 882= 53

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