Question

find the sum of all natural numbers between 1 and201 which are divisible by 5

Answer 1

here first term = 5 , last term =195 , no of terms= 38
So by using formula of AP,
S = N/2(a+l)
=38/2(5+195)
=19*200
=3800

Answer 2

Answer:

4100

Step-by-step explanation:

The natural numbers between 1 and 201 which are divisible by 5 is shown below

5, 10, 15, 20.........200

It forms an AP with a = 5, d = 5 and l = 200

Using the formula,

$t_n=a+(n-1)d\\\200=5+(n-1)5\\\\195=(n-1)5\\\\n-1=39\\\\n=40$

Therefore, the sum is given by

$S=\frac{n}{2}(a+l)\\\\S=\frac{40}{2}(5+200)\\\\S=4100$

Thus, the required sum is 4100