# Simple interest help!

• Apr 17th 2012, 07:47 AM
Aroperalta
Simple interest help!
Simple interest earned on a sum of money for 4 yrs at 7.5% p.a. exeeds that on the same sum for 3 1/2 yrs at 8% p.a. by \$90.
A) find the original sum of money
B) if the original sum of money accumulates to \$4612.50 in 5 months at simple insterest, find the interest rate per annum
• Apr 17th 2012, 08:39 AM
biffboy
Re: Simple interest help!
It's worth learning the formula I=PRT/100 for simple interest. Let y be the original sum (P in the formula stands for principal, that is original sum)

So yx7.5x4/100 - yx8x3.5/100=90

For 2nd part rearrange the formula to give R =(100I)/(PT) and put in I (which you can now work out) P (which is your answer to the 1st part) and T=5/12
• Apr 18th 2012, 01:26 PM
Wilmer
Re: Simple interest help!
Biff, please don't use x as multiplication sign; use *
• Jul 30th 2012, 05:51 AM
davidthompson873
Re: Simple interest help!
I agree with Wilmer because we might miss read it as a Variable not a multiplication sign.