Question

Find the sum of those integers between 1 and 500 which are multiples of 2 and 5.

Answer 1

integers between 1 and 500 which are multiples of 2 and 5 are 10,20,30,40........490

here a = 10 , d = 10 and last term = 490

therefore,

$sum \: = \frac{49}{2} (10 + 490) \\ = \frac{49}{2} \times 500 \\ = 49 \times 250 \\ = 12250$