<TO-DETERMINE> To calculate: The total amount invested at rate 3%, 4% and 5%. </TO-DETERMINE> <ANSWER> Solution: The total amount invested at rate 3%, 4% and 5% is 400,500 and 1600 respectively. </ANSWER> <EXPLANATION> Given information: Elena receives $112 per year from three investments totalling $2500. Part is invested at 3%, part at 4% and part at 5%. There are $1100 more invested on 5% that at 4%. Formula Used: Use elimination and substitution method. Calculation: Consider the amount invested at 3% as x , the amount invested at 4% at y and the amount invested at 5% as z . Since, the total amount invested is $2500. Therefore, the first equation becomes, 2500 x y z Since the sum of the interest earned from the three amounts is $112, write the second equation as: 0.03 0.04 0.05 112 x y z It is given that the amount invested at 5% was $1100 more than the invested at 4% interest rate. Therefore, the third equation will become: 1100 y z
Thus, the system of linear equation will be written as: 2500 1 0.03 0.04 0.05 112 2 1100 3 x y z x y z y z
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