This activity uses addition, subtraction, and the concept of integers in a real-life context.
The students need to understand the concept of what happens when you subtract a bigger number from a smaller number: “What happens when you get less than zero?” “Can you get less than zero?” and so on.
Money is a nice way to introduce the idea of negative numbers because most students have some concept of being in debt or owing someone money. You could combine this with a number line. For example: “You have $5. You owe your mother $10 and want to pay her back. You give her the $5. How much money do you have now? (You actually have $0, but you still owe your mother $5, so you are $5 in debt.) Show this on a number line.”
Questions 3c and d introduce the idea of negatives in a nice gentle way. The answers say Georgia needs $5 more to pay her bills rather than saying Georgia has minus $5 or is $5 in debt. You could ask the students to demonstrate Georgia’s situation on a number line, which would introduce the idea of negative numbers if you don’t use the scenario above.

Answers to Activity

1. $3
2. a. None
b. He would have $20 left.
3. a. Yes. Frank has $18 worth of bills and $19 cash.
b. Yes. Sally has $21 worth of bills and $25 cash.
c. No. Georgia needs $5 more to pay her bill.
d. No. Charlotte needs $9 more to pay her bills.