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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