Suppose your grandfather put $10,000 in the bank in 1965 at an annual interest rate of 7%. Using the Rule of 70, approximately how large should the bank balance be in 2015?
A)$50,000
B)$60,000
C)$80,000
D)$320,000

Question

Quizplus · Accepted Answer

The Rule of 70 estimates that the investment will double approximately every 10 years (70/7 = 10). From 1965 to 2015 is 50 years, so the investment doubles 5 times: $10,000 → $20,000 → $40,000 → $80,000 → $160,000 → $320,000.

Suppose Your Grandfather Put $10,000 in the Bank in 1965