To double takes, don't ask me why, 70/x years where x is the interest rate, so 14 years give or take a month or two.
12 years.
12 years
It will take 18 years.
About 13 years at 5.5%
17 years
Prices will double in approximately 24 years with a three percent rate of inflation.
If the interest rate was eight percent, it would take about 9 years to double your principle.
Nine years at 8%
As a rough guide to double any amount compounded annually, divide 70 by the interest rate. In this case that is 14 years.
Six years at 12%
Twelve years at 6%
Nine years at 8%