Question

find the sum of all natural numbers from 1 to 200 1) which are divisible by 7​

Answer 1

Answer:

We have to find sum 4+8+12+...+200

Clearly, it is arithmetic progression.

Here, a=4,d=4

Let there are n terms and 200 is nth term. Then,

a+(n−1)d=200

⇒4+(n−1)4=200

⇒(n−1)4=196

⇒(n−1)=49

⇒n=50

Therefore,

S

50

=

2

50

[4+200]

⇒S

50

=25×204=5100