SOLUTION: Kate has a t-shirt business that has earned a total of $15 000 this year. She invests part of the
money at 4% per year and the rest at 5% per year. After one year she earned $690
Algebra.Com
Question 1169392: Kate has a t-shirt business that has earned a total of $15 000 this year. She invests part of the
money at 4% per year and the rest at 5% per year. After one year she earned $690 in interest.
How much did she invest at each rate?
Found 3 solutions by The Troll Kid, Solver92311, greenestamps:
Answer by The Troll Kid(22) (Show Source): You can put this solution on YOUR website!
Answer by Solver92311(821) (Show Source): You can put this solution on YOUR website!
If a portion of 
monetary units are invested at 
per calendar period and the balance at 
per calendar period and the entire investment earns 
monetary units in interest for one calendar period, then if 
represents the portion of the investment earning interest, the amount invested at each rate can be calculated by solving:
\ =\ I)
for and then calculating 
John
My calculator said it, I believe it, that settles it
From
I > Ø
Answer by greenestamps(13200) (Show Source): You can put this solution on YOUR website!
A quick and easy non-algebraic method for solving this kind of problem....
(1) All $15,000 invested at 4% would yield $600 interest; all at 5% would yield $750 interest.
(2) The actual interest, $690, is 90/150 = 3/5 of the way from $600 to $750. (Picture the 3 numbers on a number line if it helps....)
(3) Therefore, 3/5 of the total was invested at the higher rate.
ANSWER: 3/5 of the $15,000, or $9000, at 5%; the other $6000 at 4%.
CHECK: .05(9000)+.04(6000) = 450+240=690
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