Question

The first term of an A.P. is 2 and common difference is 4. The sum of its 40 terms will be [MNR 1978; MP PET 2002]
A) 3200 B) 1600 C) 200 D) 2800

Answer 1

Hey there!

a = 2
d = 4 .

$S_{n}$ = n/2 [ 2a + ( n - 1 ) d ]

Now,
$S_{40}$

= 40/2 [ 2a + ( 40- 1 ) d ]

= 20 [ 2(2) + 39 ( 4 ) ]

= 20 [ 4 + 156 ]

= 20 [ 160 ]

= 3200 .

Option A is correct !

Hope helped!