Question

find the sum of 40 positive integers divisible by 6

Answer 1

Here a =6
d= 6
n= 40
Now put this value in formula
Sn =n/2 [2a + (n-1)d]
and solve
Answer wil be
4920

Answer 2

6+12+18+...... Uptown 40 terms

Sn = n/2 [2a + (n-1)d]
=40/2 [12+ (40-1)6]
=20 X 246
=4920