SOLUTION: Sally invested $6000, part at %6 simple interest and a part at 4% simple interest for a period of 1 year. how much did she invest at each rate if each account earned the same inter

Question 908566: Sally invested $6000, part at %6 simple interest and a part at 4% simple interest for a period of 1 year. how much did she invest at each rate if each account earned the same interest?
Answer by richwmiller(17219) (Show Source): You can put this solution on YOUR website!
We know the total amount of money invested. $6000
x+y=6000,
We know that the difference in interest earned by the two accounts is $0
0.04*x-0.06*y=0
x=6000-y
We substitute for x
0.04*(6000-y)-0.06*y=0
We multiply out
240-0.04y-0.06*y=0
We combine like terms.
240=0.1*y
Isolate y
y=240/0.1
y=2400 at 6%
Calculate x
x=6000-2400
x=3600 at 4%
Interest earned at 4% is 144
Interest earned at 6% is 144
We check
0.04*3600-0.06*2400=0
144-144=0
0=0
Since this statement is TRUE and neither amount is negative then all is well

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