Question

The first term and the common difference of an A. P. is 10,000 and
2000 resectively. Find the sum of first 12 terms of the A.P.

Answer 1

a = 10,000, d = 2000 , S12 = ?

`S_n = n/2[2a+(n-1)d]`

`∴ S_12 = 12/2 [2xx10,000+(12-1)xx 2000]`

             `=6(20,000+11 xx 2000)`

           `=6(20,000 + 22,000)`

           `= 6xx42,000)`

           `=2,52,000`