Find the sum of all natural numbers between 300 and 500 which are divisible by 11.

Find the sum of all natural numbers between 300 and 500 which are divisible by 11.
A.7337
B.7227
C.7447
D.7557

Ans: B
Explanation:
It makes an arithmetic progression.
Sum =1/2 n (a+l) 
a- first term
l- last term
n- no of terms

In this case a=308 , b=495 
( The smallest and largest numbers between 300-500 which are exactly divisible by 11)

To find n:
500-300=200
200/11 = 18 (Don't mind about remainder)
Therefore n=18

Substituting the values in the formula,
1/2 18 (308+495)=9*803=7227