Question

The sum of 15th term of ap is 600 and the common difference is 5 . Find the first term of an ap?

Answer 1

given The sum of 15th term of ap is 600

d=5

15/2(2*a+14*5)=600
or (2*a+14*5)=80
or 2a=80-70
or a(¹st term)is 10/2=5

5 is right answer..