plug in the values and solve for r. You will have to use some algebra skills. Is that what you are having difficulty with?

13% 1900(1+.13)^2 rounding down from 2426.11

A is $2424, P is $1900, t is 2 years. I assume your issue is that you don't know how to deal with the exponent. Take the P over.

A/P = (1+r)^t Then take log of each side.

log(A/P) = log(1+r)^t = t*log(1+r)

If you have a TI-83 a possible solution is going to Y= on the top of the calc. Then putting 2424-1900(1+X)^2 then press 2nd key and tblset, at table setup put tbl start at 0 and tbl scale at .01 (for every whole 1%) 2nd key again and look at the table for the closely answer

I missed a bracket, it should be log[(1+r)^t]

@Tom: I already plugged in the values. But it's been a few months since I've done math, and I reached a dead end with the algebra (I think).

You will want to learn as Jam describes, if you don't have calcs on your test, quiz, or whatnot, I also suggest perhaps to look up compounding and algebra on youtube

You don't need to use logarithms.

2424 = 1900 * (1 + r) ^ 2
(1 + r) ^ 2 = 2424 / 1900 ~= 1.276
1 + r = sqrt(1.276) = 1.130

So the interest rate is 13%.

You don't need to use logarithms, if you haven't learned 'em yet. Here's your equation:
2424 = 1900 (1+r) ^ 2
Divide both sides by 1900:
2424/1900 = (1+r) ^ 2
Square root of both sides:
(2424/1900) ^ 0.5 = 1+ r
So, r =[(2424/1900)^0.5] - 1 = 0.129
Rounding up, 13% interest is the minimum rate needed to make 1900 into 2424 in two years.

sorry, t broadley beat me to it

@airborne....Giving him the solution with a calculator is **exactly** why he can't do math....

Hyperactive *showed* the math. + Pi to Hyperactive Jam!

(shrug) just trying to help

If people are asking homework problems, guys, it is best to give them hints instead of the answer. The whole "Give a man a fish, he eats for a day, teach a man to fish and he eats for a lifetime."

Though, the variation of the line, which doesn't apply and is off topic is a favorite of mine "Give a man a fire and he cooks for a day. Light a man on fire and he cooks for the rest of his life!"

Anyway, as a father of three that has children with homework, I can tell you it is better to guide than just give an answer.
What I would have done was ask if he knows his algebraic principles (Mirror principle that says if 1=1, then 2+1 = 1+2... basically it is ok to do something to one side as long as you do it to the other as well), then worked on how to use roots to cancel out the exponent.... Hopefully you learned something from the answer and maybe a little knowledge from my explanation, Conservative Man?

+3 "cooks for the rest of his life"!

Oh, you do the log of each side. I was making it more complicated thatn it actually was.

gotta love logarithms. You'll really love em when you start differential equations...

+1 to Tru Ninja.
Hooray for calculus.

Re: Graphing Calculators:

Real men use RPN : )

@abgemacht:

Real men use Excel.

Real men do it by hand.

Real men let the girl do it by hand.

Real men do the girl by hand.

Real men talk about their feelings.

Thank you, Hyperactive. You just changed my sex life.

Pi ? - Go for Tau