Question 78415
Charlie won $50,000 on the 'Cash 5' Lottery adn decided not to spend any of it!  Instead he invested some of the money in bonds paying 4%, twice as much in stock paying 5%, and the remainder in a certificate paying 7%.  If the total interest earned from these three investments is to be $2,730, how much is he investing in the certificate?
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Let amt invested at 4% be "x" : interest on this is 0.04x dollars
Amt invested at 5% is "2x" ; interest on this is 0.05(2x)=0.10x dollars
Then "50,000-x-2x" is invested at 7%; interest on this is 0.07(50,000-2x)dollars
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EQUATION:
int + int + int = 2730 dollars
0.04x + 0.1x + 0.07(50,000-3x)=2730
4x+10x+7(50,000-3x)=273000
-7x+350000=273000
-7x=-77000
x=11000 (amt invested at 4%)
2x=22000 (amt invested at 5%)
50000=3x=17000(amt invested at 7%)
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cheers,
Stan H.