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Money is invested at two rates of interest. One rate is [tex]$8\%$[/tex] and the other is [tex]$5\%$[/tex]. If there is [tex]$\$[/tex]1100[tex]$ more invested at $[/tex]8\%[tex]$ than at $[/tex]5\%, find the amount invested at each rate if the total annual interest received is [tex]$\$[/tex]530[tex]$. Let $[/tex]x[tex]$ be the amount invested at $[/tex]8\%[tex]$ and $[/tex]y[tex]$ be the amount invested at $[/tex]5\%[tex]$.

The system that models the problem is:

\[ \begin{cases}
x = y + 1100 \\
0.08x + 0.05y = 530
\end{cases} \]

Solve the system using the method of addition.

\[\$[/tex] \ \_\_\_\_ \ \text{invested at } 8\% \]
[tex]\[\$ \ \_\_\_\_ \ \text{invested at } 5\% \][/tex]

Sagot :

To solve the problem, we need to determine the amounts invested at two different interest rates given a set of conditions. Let [tex]\( x \)[/tex] be the amount invested at [tex]\( 8\% \)[/tex] and [tex]\( y \)[/tex] be the amount invested at [tex]\( 5\% \)[/tex]. We are given the following conditions:

1. There is \[tex]$1100 more invested at \( 8\% \) than at \( 5\% \): \[ x = y + 1100 \] 2. The total annual interest received from both investments is \$[/tex]530:
[tex]\[ 0.08x + 0.05y = 530 \][/tex]

Now, let's solve the system of equations step-by-step using the method of addition.

Step 1: Substitute the expression for [tex]\( x \)[/tex] from the first equation into the second equation.

Given:
[tex]\[ x = y + 1100 \][/tex]

Substitute [tex]\( x \)[/tex] in the second equation:
[tex]\[ 0.08(y + 1100) + 0.05y = 530 \][/tex]

Step 2: Distribute the [tex]\( 0.08 \)[/tex] in the equation.

[tex]\[ 0.08y + 0.08 \times 1100 + 0.05y = 530 \][/tex]

This simplifies to:
[tex]\[ 0.08y + 88 + 0.05y = 530 \][/tex]

Step 3: Combine like terms.

[tex]\[ (0.08y + 0.05y) + 88 = 530 \][/tex]

[tex]\[ 0.13y + 88 = 530 \][/tex]

Step 4: Isolate [tex]\( y \)[/tex] by subtracting 88 from both sides.

[tex]\[ 0.13y = 530 - 88 \][/tex]

[tex]\[ 0.13y = 442 \][/tex]

Step 5: Solve for [tex]\( y \)[/tex] by dividing both sides by 0.13.

[tex]\[ y = \frac{442}{0.13} \][/tex]

[tex]\[ y = 3400 \][/tex]

Step 6: Substitute the value of [tex]\( y \)[/tex] back into the first equation to find [tex]\( x \)[/tex].

[tex]\[ x = y + 1100 \][/tex]

[tex]\[ x = 3400 + 1100 \][/tex]

[tex]\[ x = 4500 \][/tex]

Therefore, the amounts invested are:
- [tex]\(\$4500\)[/tex] at [tex]\( 8\% \)[/tex]
- [tex]\(\$3400\)[/tex] at [tex]\( 5\% \)[/tex]

So the final answers are:

[tex]\[ \$4500 \text{ invested at } 8\% \][/tex]
[tex]\[ \$3400 \text{ invested at } 5\% \][/tex]
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