<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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- Fall '09
- Math, Finance, Substitution Method, Addition, Maths, Elementary algebra