If 12 is added to each term of the AP : -12,-9,-6,...,21 then
which of the following is true about the sum of all terms of the AP thus obtained ?
A) The sum will increase by 12
B) The sum will increase by 144
C) The sum will become 12 times
D) The sum will become 144 times
There are (21+12)/3 + 1 = 12 terms
so the sum will increase by 12*12 = 144