# Compound interest

• December 7th 2010, 05:32 AM
Chr2010
Compound interest
Determine the time it takes to double an investment in an account that pays interest of 4% per annum compounded quaterly.....

so far i am thinking

2A=A (1+ 0.00013) ^ 4x, but it doesnt work
• December 7th 2010, 05:55 AM
e^(i*pi)
How did you get 0.00013?

If it's compounded quarterly then you need to divide your 4% annual rate by the number of compounds (4).

$2A = A\left(1+\dfrac{0.04}{4}\right)^{4t}$