What rate of interest compounded annually is required to double an investment in 4 ​years?

Answer 1

2 = (1+r)^4

1+r = the 4th root of 2 = about sqr1.414 = about 1.19

r = 1.19- 1 = .19 = about 19% annual interest rate

to double the investment in 4 years, compounded annually