Question

Find the sum of all natural number between 250 and1000 which are exactly divisible by 3

Answer 1

First non divisible by 3 between 250-1000 is 252

last no. Is 999

using A.P formula

Tn= A+(n-1)d

999= 252+3n -3

1002-252=3n

750/3=n =n =250

sum = n/2(A+L)

=125(252+999)= 156375

Answer 2

Answer:

Step-by-step explanation:

The first no starting from 250 which is divisible by 3 is 252 and last no is 999.

So accordingly we can proceed

First we'll find no of terms:

a =252 ; d=3 ; l=999

an =a+(n_1)d

n=250

Sn= n/2(a+l)

= 15625

= Ans