Calculate the length of time for #800000 to earn # 15000 if invested at 10% per annum

Answer 1

The length of time for #800000 to earn #15000 if invested at 10% per annum is 15 years.

This can be calculated using the formula:

Time (in years) = (15000 / 800000) x 100 / 10

Time (in years) = 15

Answer 2

I don't get this question or formula because I tried it so many times but failed please help me to solve