SOLUTION: A total of $1200 is invested, partly at 3% and the rest at 5%.Find the amounts invested at each rate if the total interest is $ 54

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Question 517629: A total of $1200 is invested, partly at 3% and the rest at 5%.Find the amounts invested at each rate if the total interest is $ 54
Answer by Maths68(1474) About Me  (Show Source):
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Let
At 3% amount invested = x
At 5% amount invested = 1200-x
3%*x+(1200-x)*5% = 54
(3/100)*x+(1200-x)*(5/100)=54
(3x/100)+(1200*5)/100-(5x/100)=54
(3x/100)+(6000)/100-(5x/100)=54
Multiply by 100 both sides of the equation
3x+6000-5x=5400
-2x=5400-6000
-2x=-600
-2x/-2=-600/-2
x=300

At 3% amount invested = x = $300
At 5% amount invested = 1200-x=1200-300=$900


Check
300 * 3/100 =3*3= $9
900 * 5/100 = 9*5=$45
sum = $9+$45= $54