Rule of 70 question

Question

Sarah invests $2000 into her bank account with an annual interest rate of 0.5%. Using the Rule of 70 (NOT the exact solution!), how many years will it take for her investment to reach $4000? (Round up to the nearest whole number)

Answer 1

70/,5= 140 years to get from 2,000 to 4,000

but maybe you meant 5%? not .5%

if so then

70/5= 14 years to double