# Homework Help: Review for Final

1. Jan 12, 2005

### courtrigrad

Hello all

Just had a question about interest:

Determine how much time is required for an investmnent to quadruple if interest is earned at a rate of 7.1% compunded continuously.

Would I just use the formula $$Pe^ r^t$$? And then just substitute values (say P = 0)?

Any help is appreciated

Thanks

2. Jan 12, 2005

### courtrigrad

I dont know whether I can use the above formula.

3. Jan 12, 2005

### dextercioby

My first guess is "yes"...The key words are "compounded continuously"...

Daniel.

4. Jan 12, 2005

### courtrigrad

So

$$Pe^r^t = Pe^0.071^t$$

$$Pe^r^t = 4Pe^0^.^0^7^1^t$$

Is this right so far?

Thanks

5. Jan 12, 2005

### dextercioby

Shouldn't it be something like:

$$P(t)=P_{0}e^{0.071t}=4P_{0}$$

Daniel.

6. Jan 12, 2005

### courtrigrad

yes you are right. Then how would you solve for t? Would you initially set $$P_0$$ to any number?

7. Jan 12, 2005

### Curious3141

The $P_0$ cancels out and you're left with a simple exponential equation.

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