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Solution
Let the amount invested in Saving fund = $x million
in Money market fund = $y million
in Government bond = $z million
Total invested amount is $1.8 million
So, x+y+z=1.8 .....(equation 1)
Interest earned from saving fund in a year = amount invested * rate of interest = $0.08x million
Interest earned from money market fund = $0.04y million
Interest earned from government bond = $0.07z million
Total interest earned in a year is $0.124 million, which means,
0.08x+0.04y+0.07z=0.124 or 8x+4y+7z=12.4 (by multiplying both sides by 100).....(equation 2)
The question also states that the amount in government bond is $0.2 million more than twice the amount in money market funds, which means
z=2y+0.2 ......(equation 3)
Here we need to find x, (amount invested in savings fund)
Plug z=2y+0.2 in equation 2, so we get
8x+4y+7(2y+0.2)=12.4
or 8x+4y+14y+1.4=12.4
or 8x+18y=11.......(equation 4)
Now plug z=2y+0.2 into equation 1, and we get
x+y+2y+0.2=1.8
x+3y=1.6 ....(equation 5)
Multiply (equation 5) with -6 and add to equation 4
8x+18y= 11
-6x-18y=-9.6
__________
2x = 1.4
x=0.7
So amount invested in Saving fund is $0.7 million

