Question

find the sum of first 100 even natural numbers ,which are divisible by 5​

Answer 1

The even natural no. which are divisible by 5 are: 10,20,30......

This is an AP problem

Common difference : t2-t1, t3-t2=10

First term (a) =10

Given that n = 100 nos.

Sn= n/2 [2a + (n-1)d]

S100 = 100/2 [2*10 + (100-1)10]

S100 = 50 [20 + (99)10]

S100 = 50 [20 + 990]

S100 = 50 [1010]

S100 = 50500

Therefore the sun of the first 100 even natural numbers ,which are divisible by 5 is 50500.

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