standard_description: Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.
problem_activity: Task
Materials
Popsicle sticks and rubber bands or base-10 blocks
Paper and pencil for each student
Actions
The teacher should pose the following question to students:
Louis wants to give \$15 to help kids who need school supplies. He also wants to buy a pair of shoes for \$39. If Louis gets \$1 every day for his allowance, how many days will it take him to save enough money for both? Explain how you know.


aligns: no