SOLUTION: Mark invested $4000 at simple annual interest, some at 5% and the rest at 8%. If he received $272 in interest for one year, how much did he invest at each rate? I have absolutel

Question 697573: Mark invested $4000 at simple annual interest, some at 5% and the rest at 8%. If he received $272 in interest for one year, how much did he invest at each rate?
I have absolutely no idea how to do this problem. Can anyone help me?
Answer by lynnlo(4176) (Show Source): You can put this solution on YOUR website!
x=amount invested at 5%
y-------------------8%
x+y=$4000
.05*x+.08y=272
x=$4000-y
.05(4000-y)+.08y=272
200-.05y+.08y=272
0.03y=72
y=2400
y=2400,,,,,x=1600
$1600 at 5%
$2400 at 8%
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