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So, I have a word problem that I need to use the formula $A = Pe^{rt}$ to solve...

Suppose $2000 is invested at an interest rate 2.75% compounded continuously. What is the balance in the account after 4 years? Round answer to the nearest cent.

I know that... $$ P = \$2000\\ R = 2.75\%\\ T = 4 $$

What I'm trying to do is calculate this using my TI-83 and I believe the way to do this is by first multiplying 2.75(4), then press the $e^x$ button, plug in my answer, then multiply it by $2000$. That's my understanding of it, but what's the actual correct way to insert this problem into my calculator?

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    $\begingroup$ You wrote 2.75% above, but 2.78 in the description. Also, you need to make sure of precedence and that can vary on different implementations (and calculators). Is your equation p*(e^r)*t or pe^(rt)- as this makes a huge difference. Does this solve your problem? $\endgroup$ – Amzoti Oct 5 '12 at 2:21
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As Amzoti said, I think correct eqn is $A=Pe^{rt}$

you can plot

y=2000*e^(.0275x)

in a graph and use the 2nd Calc- Value commands to evaluate at $t=4$, or can use 2nd Table to check your for multiple ranges of $t$ (we just use $x$ in the ti-83).

the way you did it should be totally fine too, so long as you use the right formula.

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  • $\begingroup$ Alright, thanks. I tried it both ways and came up with the same answer. :) $\endgroup$ – Brandt Oct 5 '12 at 11:58

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