Question

Choose the correct answer in each of the following questions:

The sum of first 40 positive integers divisible by 6 is [CBSE 2014]

(a) 2460 (b) 3640 (c) 4920 (d) 4860

Answer 1

The positive integers divisible by 6 are 6, 12, 18, ... .

This is an AP with a = 6 and d = 6.

Also, n = 40 (Given)

Using the formula, $S_n=\frac{n}{2}\left[2a+\left(n-1\right)d\right]$, we get

$$\begin{gathered} S_{40}=\frac{40}{2}\left[2\times 6+\left(40-1\right)\times 6\right] \\ =20\left(12+234\right) \\ =20\times 246 \\ =4920 \end{gathered}$$

Thus, the required sum is 4920.

Hence, the correct answer is option C.