Question 208811
"Bill invested three times as much money at 9% as at 7.5%. 
If he wanted his interest at the end of the year to be $1725, 
what amount of money should he invest a 7.5%?" 
;
Let x = amt invested at 7.5%
then "three times as much money at 9% as at 7.5%" therefore:
3x = amt invested at 9%
;
Write the interest equation:
.09(3x) + .075x = 1725
.27x + .075x = 1725
.345x = 1725
x = {{{1725/.345}}}
x = $5000 invested at 7.5%
:
:
Check solution (15000 invested at 9%)
.09(15000) + .075(5000) = 
1350 + 375 = 1725