Numbers - General Aptitude

Q1:

The sum of even numbers between 1 and 31 is:

A 6

B 28

C 240

D 512

ANS:C - 240

Let Sn = (2 + 4 + 6 + ... + 30). This is an A.P. in which a = 2, d = 2 and l = 30 Let the number of terms be n. Then, a + (n - 1)d = 30      2 + (n - 1) x 2 = 30     n = 15.

Sn = n (a + l) = 15 x (2 + 30) = (15 x 16) = 240.
2 2