Question

Juan is working two summer jobs, making $12 per hour babysitting and making $16 per hour lifeguarding. In a given week, he can work at most 17 total hours and must earn at least $240. If Juan worked 3 hours babysitting, determine all possible values for the number of whole hours lifeguarding that he must work to meet his requirements. Your answer should be a comma separated list of values. If there are no possible solutions, submit an empty answer.

Answer 1

\text{Let }b=

Let b=

\,\,\text{the number of hours babysitting}

the number of hours babysitting

\text{Let }l=

Let l=

\,\,\text{the number of hours lifeguarding}

the number of hours lifeguarding

\text{\textquotedblleft at most 17 hours"}\rightarrow \text{17 or fewer hours}

“at most 17 hours"→17 or fewer hours

Use a \le≤ symbol

Therefore the total number of hours worked in both jobs, b+lb+l, must be less than or equal to 17:17:

b+l\le 17

b+l≤17

\text{\textquotedblleft at least \$240"}\rightarrow \text{\$240 or more}

“at least $240"→$240 or more

Use a \ge≥ symbol

Juan makes $12 per hour babysitting, so in bb hours he will make 12b12b dollars. Juan makes $16 per hour lifeguarding, so in ll hours he will make 16l16l dollars. The total amount earned 12b+16l12b+16l must be greater than or equal to \$240:$240:

12b+16l\ge 240

12b+16l≥240

\text{Plug in }\color{green}{3}\text{ for }b\text{ and solve each inequality:}

Plug in 3 for b and solve each inequality:

Juan worked 3 hours babysitting

\begin{aligned}b+l\le 17\hspace{10px}\text{and}\hspace{10px}&12b+16l\ge 240 \\ \color{green}{3}+l\le 17\hspace{10px}\text{and}\hspace{10px}&12\left(\color{green}{3}\right)+16l\ge 240 \\ l\le 14\hspace{10px}\text{and}\hspace{10px}&36+16l\ge 240 \\ \hspace{10px}&16l\ge 204 \\ \hspace{10px}&l\ge 12.75 \\ \end{aligned}

b+l≤17and

3+l≤17and

l≤14and

​  

 

12b+16l≥240

12(3)+16l≥240

36+16l≥240

16l≥204

l≥12.75

​  

 

\text{The values of }l\text{ that make BOTH inequalities true are:}

The values of l that make BOTH inequalities true are:

\{13,\ 14\}

{13, 14}

\text{(the final answer is this entire list)}

(the final answer is this entire list)