Question

A certain investment takes 18 years to grow 5 times.
How long would it take to double itself? What annual
rate of simple interest does the investment earn?​

Answer 1

rate r = 100xI/pn. (I interest, P principal, n=no. of yrs)

r = 4px 100/px 18=22 2/9%

n =.px loox9/px 200=4.5 yrs

Rate 22 2/9% and period: 4.5 yrs