Hello Paramjit
Answer is 960
As it is a arithmetic progression.( Ap series).
Formula for the sum of all terms is
Sum= (n/2) * ( 2*a + (n-1)* d)
Where n= number of terms
a = first term of series
d = difference between any two consecutive terms.

Hi paramjit , its problem of arithmetic progression. So use the formula mentioned below

n/2(2a+(n-1)d)

Thanks.