Question 1099037
quadruple is $4000
4000=1000(1+.015)^n
4=1.015^n
ln4=n1n (1.015)
n=93.1 years
rule of 72: doubling time is 72/interest rate=48 years
quadrupling is doubling of doubling, and that would be two doublings or 96 years, a good approximation.