The Stamp Collection
Alignments to Content Standards:
3.OA.D.8
Task
Masha had $120$ stamps. First, she gave her sister half of the stamps and then she used three to mail letters. How many stamps does Masha have left?
IM Commentary
This task uses language, "half of the stamps," that students in Grade 5 will come to associate with multiplication by the fraction $\frac12$. In Grade 3, many students will understand half of 120 to mean the number obtained by dividing 120 by 2. For students who are unfamiliar with this language the task provides a preparation for the later understanding that a fraction of a quantity is that fraction times the quantity.
Solution
We can visualize the problem with a bar diagram:
2 units = 120
1 unit = 60
60 - 3 = 57
Masha had 57 stamps left.
The Stamp Collection
Masha had $120$ stamps. First, she gave her sister half of the stamps and then she used three to mail letters. How many stamps does Masha have left?