Needing help with a math problem...

Race Mom, ASN, RN · Sep 20, 2005

I took NLN 5 years ago and there weren't any questions like that. Maybe exponents, but not compounding interest.

Lisa

Daytonite, BSN, RN · Sep 20, 2005

Sounds like you've gotten your answers. With these compound interest problems you have to keep the "time" part of the formula equation is years. So, nine months is 9/12th's of a year. The exponent you need on the formula is the product of the number of compoundings per year (12) and the 9/12th of a year (or 0.75). In your formula n is always going to be 12, not 9.

Fugitive · Sep 21, 2005

Sounds like you've gotten your answers. With these compound interest problems you have to keep the "time" part of the formula equation is years. So, nine months is 9/12th's of a year. The exponent you need on the formula is the product of the number of compoundings per year (12) and the 9/12th of a year (or 0.75). In your formula n is always going to be 12, not 9.

You're completely correct.

That is the way that jaysma originally set up the problem, but had the incorrect answer.

I just assumed that the math was done incorrectly so I tried to solve it another way.

Jaysma, the way you originally set up the problem is the correct way to solve it. Redo your calculations and you should get the correct answer of $7006.74

I redid your work and that's what I got.

I guess I should have just double checked what you did originally instead of thinking maybe you set it up wrong. Haha!

What is $6800 at 4% compounded monthly for 9 months?
I have
6800(1+.04/12)12x.75exponent
6800(this is where I have trouble since the 3 is repeating)(1.003)9exponent
=$6985.82
The study guide says the correct answer is $7006.74. I think I messed up with the .04/12 since you get a repeating 3. What do you do with it?

jaysma · Sep 21, 2005

Well I got my test back today. First of all, the teacher walks into the classroom and tells us (class of 32 students) that in her 7 years of teaching she has never seen a class do so poorly on chapter 6 (it's a fast-track course btw). The class average was 52.4% She said that the highest score was 80%. She handed back the tests and I made an 80%. I felt horrible for scoring so low (my average in the class was a 96.9%), but I also felt good since I wasn't one of the many who flunked it!

Anyway, we went over the whole test today and she's letting us re-test tomorrow, but no multiple choice this time. The average between the 2 will be our test grade.

Fun2, BSN, RN · Sep 21, 2005

It seems your instructor didn't quite get the point across this time.:uhoh21: Good job on making that 80%!!!

Study hard, and maybe you can get that average back up. If not, be happy knowing you passed it!!!!!!!! :)

Good luck!!!

Well I got my test back today. First of all, the teacher walks into the classroom and tells us (class of 32 students) that in her 7 years of teaching she has never seen a class do so poorly on chapter 6 (it's a fast-track course btw). The class average was 52.4% She said that the highest score was 80%. She handed back the tests and I made an 80%. I felt horrible for scoring so low (my average in the class was a 96.9%), but I also felt good since I wasn't one of the many who flunked it!
Anyway, we went over the whole test today and she's letting us re-test tomorrow, but no multiple choice this time. The average between the 2 will be our test grade.

utahliz · Sep 22, 2005

The exponent should not be 9x0.75, it should be 12x0.75, which is 9. Think of it this way: every time the interest is compounded, the principal at the beginning of the period is multiplied by 1.00333.... So if it is compounded 9 times, the exponent should be 9. You arrive at it by multiplying the number of compounding periods in a year (12 months in this case) by the number of years total for which interest accrues (0.75 in this case).

I hope this makes sense. I'm an engineer-turned-nurse, but my son says I don't explain math very well. I think it's just intuitive for me. But it's always helped me to think about the meaning of what I'm doing. Jaysma, your only error is rounding the 1.003333... to 1.003. When you get the repeating numbers, use all the digits that your calculator will hold (usually 8).