Mathematics

Problem

Two different infinite geometric series share the same common ratio

r

with

|r|<1

. The first series has sum

40

. The first term of the second series exceeds that of the first series by

5

, and the second series has sum

60

. What is

r

? a)

\tfrac{7}{8}

\tfrac{3}{4}

\tfrac{4}{5}

\tfrac{2}{3}