Question

8 terms are inserted between 5 and 43 so that the resulting sequence is an AP. The sum of the resulting AP is. [3 MARKS]

Answer 1

Including the terms 5 and 43, the number of terms in the AP will be 10.

Now, the first term of the AP is 5 and the last term is 43. [1 Mark]

The sum of n terms of an AP is given by
$S_n=\frac{n}{2}(firstterm+lastterm)$ [1 mark]

Hence,
$S_{20}=\frac{10}{2}(5+43)=5\left(48\right)=240$ [1 mark]