basically here you have to compute
where you don’t know x and where a=5 and V=1,5.
For relative low interest rates and periods, the simpler process for precise results is the following:
1) Calculate what would be the solution with simple interest – in this case, 10%; the real result will always be lower than that
2) Decrease by 1 percentage point – in this case, 9%
3) Apply Taylor series till the third element. To do so, you would have to learn by art the following formula:
Given point 2, x=9%
4) Repeat decreasing till when you find a value below V=1.5
Thus the result is between 8% and 9%.
Hope this helps,