Algebra
posted by lobna on .
An investment of $54,000 was made by a business club.The investment was split into three parts and lasted for one year.The first part of the investment earned 8% interest, the second 6%, and the third 9%. Total interest from the investments was $ 4260. The interest from the first investment was 6 times the interest from the second. Find the amounts of the three parts of the investment.
x * 0.08 y* 0.09 z* 0.06 = 4260 I multiply by 100 (1)
8x+9y+6z=426,000 (1)
8x+6(9y)=0 (2)
8x+54y=0 (2)
x+y+z=54,000 (3)
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8x+9y+6z=426,000 (1)
x+y+z=54,000 (3) *6
6x6y6z=324000 (4)
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8x+9y+6z=426,000 (1)
6x6y6z=324000 (4)
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2x+3y=102000 (5) *4
8x12y=408000
8x+54y=0 (2)
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42y=408000
y= 68000/7 I find the y
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is that correct ?

how can y be negative?
x+y+z = 54000
.08x + .06y + .09z = 4260
.08x = 6*.06y
x,y,z = 36000, 8000, 10000

So, where did you go wrong?
8x+6(9y)=0
Why do you think the interest sums to zero?