Question

Jeanne babysits for $6 per hour. She also works as a reading tutor for $10 per hour. She is only allowed to work 20 hours per week. This week, her goal is to make at least $75.
A. Use a system of inequalities to model the scenario above. Let x represent babysitting hours and y represent tutoring hours.
B. Use the model created in part A to create a graph representing Jeanne’s probable income earned and possible number of hours worked this week.
C. Analyze the set of coordinate values that represent solutions for the model created in part A. Choose one of the coordinates within the solution and algebraically prove that the coordinate represents a true solution for the model.

Answer 1

A) System of inequalities

Income from babysitting: 6x
Income from tutoring: 10y

Goal for this week: at least $ 75 => 6x + 10y ≥ 75
Number of hours: maximum $20 => x + y ≤ 20

x and y have to be zero or positvie => x≥0 and y ≥ 0

Answer of part A.

6x + 10y ≥ 75
x+y ≤ 20
x ≥ 0
y ≥ 0

Part B. Graph

The solution is a region closed by 4 lines and you can find it in the file attached.

In that graph:

1) the line x + y = 20 is the upper limit
2) the line 6x + 10 y = 75 is the lower incclined line
3) y = 0 is the botton horizontal line it is the x-axis
4) x = 0 is the left vertical line, in is the y-axis

Part C.

Use, for example the point (7,10).

It is in the region of the graph limited by the above equations.

It implies:

Number of hours worked = 7 + 10 = 17 which is less than 20.

Income: 6(7) + 10(10) = 42 + 100 = 142, which is greater than 75

Of course, both are greater than 0.

In this way we proved that the point (7,10) is a true solution for the model.

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