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Gigazombie Cybermage
Registered User, __BANNED USERS regular

Me again, with more math problems. I'm on financial formulas, and I'm about to claw my own eyeballs out in frustration.

$45.67 at 3.5% compounded daily interest for 3 years. Now, it should look like this; 45.67(1+3.5/365)^(365*3), right? But I get a nonsensical number; 1577605.40. That's way too big to be right, isn't it? I'm so frustrated. I've never been taught this stuff and now I'm on the verge of failing math class. Trying to find the future value.

$45.67 at 3.5% compounded daily interest for 3 years. Now, it should look like this; 45.67(1+3.5/365)^(365*3), right? But I get a nonsensical number; 1577605.40. That's way too big to be right, isn't it? I'm so frustrated. I've never been taught this stuff and now I'm on the verge of failing math class. Trying to find the future value.

## Posts

A=P(1+(r/m))^rt

We just got through compounded interest in business math, and I struggled with it as well, but it's not so bad and I'd be happy to try and help you get through it too!

"If the half-life of (whatever) is 25 years, find the decay constant r."

Do I just assume it starts from 100 mg?

Gigazombie Cybermageon50=100e^r(35)

0.5=e^35r

35r/35=ln0.5/35

r=ln0.5/35

r=-0.0198 (Had to round it to 4 decimal places)

Is this right?

You need to be paying closer attention to what you are doing, because you have 35 years in one place and say 25 years in another. Which one is it?

Also, the decay constant should be positive if it is actually decreasing in value over time. Look over http://en.wikipedia.org/wiki/Exponential_decay or http://en.wikipedia.org/wiki/Half-life to see some examples of the formulas and derivations that seem like they may be relevant on this subject.

Does this look okay?

600(((1+0.06(1/4))^(4(20))

Trying to find an investment deposited quarterly, compounded quarterly after twenty years at 6%

I got $12,736.36 as an answer

Gigazombie CybermageonYou should look into a tutor. Most colleges have some sort of learning center that can set you up with someone, and it's free of charge. Actually that's not true, it's paid for out of your tuition expenses, so you're already paying for a tutor anyway.

You're typing something in wrong somewhere when computing it, which you should notice because that number looks like it should be rather too high for 20 years of compounding interest on $600. The future value of 600 after 20 years compounded quarterly is $1974.40. Which is 600*((1.015)^80).

The formula you have quoted assumes an individual has made an initial investment (of 600 bucks), and that investment is earning interest on it (or rather that's what it loos like to me). If you are told that a person is making periodic deposits into an account, that is earning interest at a certain rate, you want to use a different formula. I'd have to dig up old Business Math formula sheets (as I can rarely remember them myself), but what you have quoted isn't it.

Generally (at least in my graduate radiation courses) the decay constant is given as a positive value, the negative sign is added in the formula

N(t) = N(0)e^-[(decay constant)*(time)]

y2jake215onmaybe i'm streaming terrible dj right now if i am its here