After how many months will Rita pay two hundred dollars in simple annual interest on a credit card that charges fifteen percent on her four hundred dollars balance?

Question

anonymous · Answer

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anonymous · Answer

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anonymous · Answer

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anonymous · Answer

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anonymous · Answer

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anonymous · Answer

interest=p*r*t/100
$$200=\frac{ 400*15*t }{ 100 },t~ is~ \in~ years$$

anonymous · Answer

T is what?

anonymous · Answer

t is time.

anonymous · Answer

Oh, okay.

anonymous · Answer

yeah t is time p is principal i is intrest r is rate

anonymous · Answer

So what do I do?

anonymous · Answer

i=p*r*t

anonymous · Answer

correct

anonymous · Answer

$$t=\frac{ 200 }{60 }=\frac{ 10 }{ 3 }*12=40~ months.$$

anonymous · Answer

but 40 months is how many years?

whpalmer4 · Answer

You could probably work this out in your head.  15% annual simple interest is 15%/12 = 1.25% simple interest each month, or $1.25/$100 balance * $400 balance = $5/mo.  $200/($5/month) = 40 months.

whpalmer4 · Answer

1 year = 12 months

1 year/12 months = 1

40 months * (1 year/12 months) = 40/12 years = 
(you can reduce the fraction or make a decimal)

whpalmer4 · Answer

problem does ask for "how many months", I note...

anonymous · Answer

so once you find the time in years you apply the number to the formula and BAM!!! you will have your answer

whpalmer4 · Answer

no, you work it in months because you have monthly interest.

anonymous · Answer

ok maybe I was wrong but I'm only in 6th grade so...

whpalmer4 · Answer

Well, you could work it in years as well, since you have simple interest in this problem.  If the problem dealt with compound interest, you couldn't.  

Anyhow, any questions about how to get the answer?