PDURATION

PDURATION(rate, pv, fv)

Returns the number of periods required by an investment to reach a specified value.

rate	The interest rate per period.
pv	The present value of the investment.
fv	The future value of the investment.

REMARKS

* This function was added in Excel 2013.
* For the Microsoft documentation refer to support.microsoft.com
* For the Google documentation refer to support.google.com

	A
1	=PDURATION(3%,9000,10000) = 3.56
2	=PDURATION(5%,50,100) = 14.21
3	=PDURATION(RRI(12,100,200),100,200) = 12.00

1 - How many periods are needed for an investment of £9,000 to reach £10,000 when you have an interest rate of 3%.
2 - How many periods are needed for an investment of £50 to reach £100 when you have an interest rate of 5%.