According to the given question we have to find the sum of natural numbers between 1 and 100 which are divisible by 2 or 5, so the sequence is 2, 4, 6…98 which are multiples of 2 and another sequence 5, 15, 25….95

To find: the sum of all - natural numbers between 1 and 100, which are divisible by 2 or 5

For the first sequence, it is an AP with first term a as 2 and common difference d as 2

Hence the sum is given by the formula

For the second sequence, it is an AP with first term a as 5 and common difference d as 10

Hence the sum is given by the formula

Hence total sum is s₁ + s₂ = 2450 + 500 = 2950