Question

The sum of all integers between 200 and 400 divisible by 9 is?

Answer 1

531 okkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk

Answer 2

The required sum is 6633.

Solution:

The numbers lying between 200 and 400, which are divisible by 9 are,

207, 216, 225, .... 396.

First term, a = 207

Last term, l = 396

Common difference, d = 9

Let the number of terms of the A.P. be n.

an = 396 = a + (n - 1) d

396 = 207 + (n - 1) 9

9 (n - 1) = 189

n - 1 = 21

n = 22

Sum of 22 = 22 / 2 (207 + 396)

= 11(603)