Question 6773: a college student earned $8800 working as a waiter. the student invested some of the money at 7% and the rest at 6%, if the student recieved a total of $560 in interest at the end of the year, how much was invested at 7%?
This is the formula I used: principal multiplied by rate = interest OR x(.07) = .07x then I added 8800 - x(.06) = 560 which showed as:
.07x + 8800 - x(.06) = 560
I tried to solve for x and got 8240. I know I'm doing something wrong. can you help?
Sandy
Answer by Earlsdon(6294)   (Show Source):
You can put this solution on YOUR website! Well, you started out ok but when you got to the line: 8800 - x(.06) = 560, this is where your mistake lies.
It should have been: (8800 - x)(.06) This is 6% of the total amount minus that invested at 7%
So, you should have:
.07x + (8800 - x)(.06) = 560 Solve for x.
.07x + (.06)(8800) - .06x = 560 Simplify.
.07x - .06x + 528 = 560
0.1x = 32
x = $3200 The amount invested at 7%
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