Question

1. find the sum of all natural numbers lying between 100 and 500 which are divisible by 8.

2. find the sum of all the three digit natural numbers which are divisible by 13.

Answer 1

This is the answer ok any doubt

Answer 2

Answer:

n = 40

Step-by-step explanation:

1) Let the first number which is divisible by 8 is 104 and last term is 496

a = 104

common difference = 8

Apply A.P formula

an = a + (n - 1) * d

496 = 104 + ( n - 1) * 8

496 - 104 = ( n - 1) * 8

392/ 8 = n - 1

39 = n - 1

39 + 1 = n

n = 40

2) First term = 104

Last term  = 987

d = 13

by putting on A.P formula you can calculate like above question.