UPSEE Solved Model Paper 6

We can solve this problem using sum of n terms of an A.P.
We know that
tn = Sn−Sn−1
By using this formula we can find the 12th term
We have
The sum of n term of a series is

n(n+1)(n+2)

3

Take the given sum as Sn
T12 = S12−S11
[Since tn = Sn−Sn−1]
here n = 12
=

12(12+1)(12+2)

3

-

11(11+1)(11+2)

3

= 4 × 13 × 14 - 11 × 4 × 13
= 728 - 572
= 156
∴ The sum of n terms of a series is

n(n+1)(n+2)

3

The 12th term is 156