Question 1

Find the average of first 30 multiples of 7.

Solution

First thirty multiples of 7 will form an arithmetic progression : 7,14,21,.......,210

First term, $$a=7$$ and common difference, $$d=7$$

Sum of $$n$$ terms = $$\frac{n}{2}(a+l)$$

=> $$S_{30}=\frac{30}{2}(7+210)$$

= $$15\times217$$

Now, average of 30 terms = $$\frac{15\times217}{30}$$

= $$\frac{217}{2}=108.5$$

=> Ans - (D)

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