Thread: Interest rate help?

1. Interest rate help?

Hello all, I am confused on where to go with this problem after a certain point.

Question- What interest rate--to at least one decimal place--compounded weekly do you need to earn to make $8000 double in 9 years? So far I have done this but not sure if it is correct- r=8000(1+r/52)^52*9 16000/8000=8000(1+r/52)^52*9 2=8000(1+r/52)^52*9 Any help would be greatly appreciated. Thank you! 2. Re: Interest rate help? Why have you put r on the LHS? It's the final amount that should go there. The rule is$\displaystyle \begin{align*} A &= P\left( 1 + R \right) ^n \\ 16\,000 &= 8000 \left( 1 + \frac{r}{52} \right) ^{52 \cdot 9 } \end{align*}\$

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