Question 91

The average of first 20 multiples of 12 is:

Solution

Here ,$$n=20$$ and first term,$$a=12$$

and last term,$$l=240$$.

(12,24,36,48,.....,240) these are the first 20 terms of the series that is multiple of 12.

So,Sum of an AP series is

$$=(a+l)n/2.$$

So, Sum of the above series would be

$$(240+12)×(20/2)=252×10=2520.$$

So, average of the sum$$=2520/20=126$$.

So, C is correct choice.

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