How much was invested in the 7% account?

Question

A total investment of $10,000 is made into two savings accounts. One account yields 7% simple interest and the other 8% simple interest. He earns a total of $765.00 interest for the year. How much was invested in the 7% account?

Answer 1

Let X = amount invested at 7%

Then the amount invested at 8% is (10000-X)  

 

The formula for simple interest is I=PRT, so the total amount of interest earned in 1 year is 

 

.07X + .08(10000-X) = 765.00

.07X + 800 - .08X = 765

-.01X = -35

X = $3500 was invested at 7%.  

 

Check:  $6500 was invested at 8%, so total interest was  

            .07*3500 + .08*6500 = 245 + 520 = $765.00