Read the following problem, set up a
2x2 system of equations.
Solve by Substitution/Matrices
One canned juice drink is 15% orange juice; another is 9%
orange juice. How many liters of each should be mixed
together to get 30 liters which is 13% orange juice?



Answer :

To solve this problem, we need to set up a system of equations and solve it to find out how many liters of each type of juice should be mixed. Let's break it down step-by-step:

1. Define the Variables:
- Let [tex]\( x \)[/tex] be the amount of the 15% orange juice (in liters).
- Let [tex]\( y \)[/tex] be the amount of the 9% orange juice (in liters).

2. Set Up the Equations:
- The total volume of the mixture should be 30 liters. Therefore, we can write:
[tex]\[ x + y = 30 \][/tex]
- The mixture should be 13% orange juice. The total amount of orange juice contributed by both types of juice should be 13% of 30 liters. Therefore, the second equation is:
[tex]\[ 0.15x + 0.09y = 0.13 \times 30 \][/tex]

3. Simplify the Second Equation:
- First, calculate [tex]\( 0.13 \times 30 \)[/tex]:
[tex]\[ 0.13 \times 30 = 3.9 \][/tex]
- So, our second equation becomes:
[tex]\[ 0.15x + 0.09y = 3.9 \][/tex]

Now we have the system of equations:
[tex]\[ \begin{cases} x + y = 30 \\ 0.15x + 0.09y = 3.9 \end{cases} \][/tex]

4. Solve the System of Equations:

Substitution Method:

- Solve the first equation for [tex]\( y \)[/tex]:
[tex]\[ y = 30 - x \][/tex]
- Substitute [tex]\( y \)[/tex] in the second equation:
[tex]\[ 0.15x + 0.09(30 - x) = 3.9 \][/tex]

- Simplify and solve for [tex]\( x \)[/tex]:
[tex]\[ 0.15x + 2.7 - 0.09x = 3.9 \][/tex]
[tex]\[ 0.06x + 2.7 = 3.9 \][/tex]
[tex]\[ 0.06x = 1.2 \][/tex]
[tex]\[ x = \frac{1.2}{0.06} = 20 \][/tex]

- Now, substitute [tex]\( x = 20 \)[/tex] back into the first equation to find [tex]\( y \)[/tex]:
[tex]\[ y = 30 - 20 = 10 \][/tex]

So, the solution to the system is:
- [tex]\( x = 20 \)[/tex] liters of the 15% orange juice
- [tex]\( y = 10 \)[/tex] liters of the 9% orange juice

Therefore, you should mix 20 liters of the 15% orange juice with 10 liters of the 9% orange juice to get 30 liters of a mixture that is 13% orange juice.

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