SOLUTION: Mr. Jones has $16,000 to invest. He invests part at 9% and the rest at 10%. If he earns $1,510 in interest after 1 year, how much did he invest at each rate?

Question 1154013: Mr. Jones has $16,000 to invest. He invests part at 9% and the rest at 10%. If he earns $1,510 in interest after 1 year, how much did he invest at each rate?
Found 2 solutions by mananth, ramkikk66:
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Investment I 9.00% per annum $x
Investment II 10.00% per annum $y

x + y 16000 ------------------------1
9.00% x + 10.00% y = 1510
Multiply by 100
9 x + 10 y = 151000 --------2

Multiply (1) by -10
we get

-10 x -10 y = -160000.00

Add this to (2)

-1 x+ 0 y = -9000.00

divide by -1

x = 9000 investment at 9%
Balance 7000 investment at 10%

CHECK Interest
9000 810
7000 700
Total 1510

Answer by ramkikk66(644) (Show Source): You can put this solution on YOUR website!
Total money = 16000
Let x dollars be invested at 9%. So 16000 - x dollars would be invested at 10%.
Interest on the 1st part = x * 0.09
Interest on the 2nd part = (16000 - x) * 0.1
Total interest = 1510 (given)
i.e.
expanding

moving variables and constants to either side of the equation

i.e
Amount invested at 9% = 9000, interest earned = 9000 * 0.09 = 810
Amount invested at 10% = 16000 - 9000 = 7000, interest earned = 7000 * 0.1 = 700
Total interest = 810 + 700 = 1510, check!
Ans:
dollars invested at 9%, dollars invested at 10%.

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