Question

The third term of an ap is 10 more than the first term while the fifth term is 15 more than the second term,find the sum of the 8th and 15 term of the ap,if the seventh term is seven times the first term.

Answer 1

a+2d = a+10

so clearly, d=5
now, a+6d = 7a, so a = 5
so the sum
a8+a15 = 5+40 + 5+70 = 120