Question

Whitney invested $19,000, part at 5% and part at 7%. If the total interest at the end of the year is $1,110.,how much did she invest at 5%.

I know the answer is $11,000. I would like to know how to actually solve the equation.

Answer 1

let x = amount at 5%
19000-x = amount at 7%

Now, just add up the amount of interest, since they give you the total interest:

.05x + .07(19000-x) = 1110
.05x + 1330 - .07x = 1110
.02x = 220
x = 11000

So, 11000 at 5%
8000 at 7%

Answer 2

invested $1,110.00, how much was his rate of interest?