Answer:
$15,000 was invested in CDs.
$40,000 was invested in bonds.
$75,000 was invested in stocks.
Step-by-step explanation:
Let C be the amount invested for CDs, B be the amount invested for bonds, and S be the amount invested for stocks.
We know that the total amount invested must be $130,000 because that was the amount given to the Scholarship Fund. So:
[tex]C+B+S=130000[/tex]
We know that CDs pay 2% or 0.02 interest; Bonds pay 2.9% or 0.029 interest; and Stocks pay 9.9% or 0.099 interest. In total, the investment earned $8,885. So:
[tex]0.02C+0.029B+0.099S=8885[/tex]
Let's remove the decimals by multiplying everything by 1000. This yields:
[tex]20C+29B+99S=8885000[/tex]
Now, we know that $25000 more was invested in bonds than CDs. So:
[tex]B=25000+C[/tex]
We have a triple system of equations. We can solve this using substitution. Let's substitute our third equation into the second equation. This yields:
[tex]20C+29(25000+C)+99S=8885000[/tex]
We want to isolate the C variable. Here, we removed the B but we still have an S.
So, to remove the S, we can go back to our first equation. We have:
[tex]C+B+S=13000[/tex]
Subtract C and B from both sides:
[tex]S=130000-C-B[/tex]
We can now substitute this for S:
[tex]20C+29(25000+C)+99(130000-C-B)=8885000[/tex]
We got a B again. But, we already know what B is. Substitute:
[tex]20C+29(25000+C)+99(130000-C-((25000)+C))=8885000[/tex]
So, our equation is now in terms of C. Solve for C. Distribute on the far right:
[tex]20C+29(25000+C)+99(130000-C-25000-C)=8885000[/tex]
Combine like terms:
[tex]20C+29(25000+C)+99(105000-2C)=8885000[/tex]
Distributive Property:
[tex]20C+725000+29C+10395000-198C=8885000[/tex]
Combine like terms:
[tex](20C+29C-198C)+(725000+10395000)=8885000[/tex]
Add:
[tex]-149C+11120000=8885000[/tex]
Subtract 1112000 from both sides:
[tex]-149C=-2235000[/tex]
Divide both sides by -149:
[tex]C=15000[/tex]
So, a total of $15,000 was invested in CDs.
Since $25,000 more was invested in bonds than in CDs, this means that a total of $25000+$15000 or $40,000 was invested in bonds.
To find out how much was invested in stocks, we can use our first equation again:
[tex]C+B+S=130000[/tex]
Substitute 15000 for C and 40000 for B:
[tex]15000+40000+S=130000[/tex]
Add:
[tex]55000+S=130000[/tex]
Subtract 55000 from both sides:
[tex]S=\$75000[/tex]
So, $15,000 was invested in CDs, $40,000 was invested in bonds, and $75,000 was invested in stocks.
And we're done!
