Question

Find the sum of an infinite G.P. whose first term is 28 and fourth terms is 4/49

Answer 1

a = 28
a(r^3) = 4/49
After dividing above equations we get r^3 = 1/243 and r = 1/7
Sum of infinite G.P. = a/(1-r)
=28 / (1 - 1/7)
=28 /6/7
=98/3