Question

Kay started a chess club, and for a while she was the only member. She planned to have each member find two new members each month. By the end of the first month, she had found two new members. If her plan is carried out, how many members will the club have at the end of 6 months

Answer 1

127

Explanation:

The sum of 7 terms of the series 1 +2 +4 +... with first term 1 and common ratio 2 is given by ...

Sn = a1 × (r^n -1)/(r -1) . . . . . . first term a1, common ratio r

S7 = 1 × (2^7 -1)/(2 -1) = (128 -1)/1 = 127

At the end of 6 months, the club will have 127 members.