School Supplies

Task

Pia takes some money to the store to buy school supplies. She buys some paper for \$3 and a pen for \$2. After she buys these supplies, she has \$7 left. How much money did Pia bring to the store?

IM Commentary

This task could be used for either instructional or assessment purposes, depending on where students are in their understanding of addition and how the teacher supports them. The solution shown is very terse; students' solution strategies are likely to be much more varied.

Solutions

Solution: Tape diagram

Students who are familiar with tape diagrams might use them to solve the problem by first drawing a picture:

and then reasoning, "If she spent \$2 + \$3 dollars and had \$7 left over, then she had $\$2+\$3+\$7=\$12$ to start."

There are many more strategies that students might use.

Solution: Using Addition with Objects

Students could use objects to add

2+3=5 5+7=12

Students who have mastered fluent addition for numbers up to 12 could also add these two quantities in their head.