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: Stage 2: Ones Cubes
Required Preparation
Materials to Gather
Base-ten blocks
Materials to Copy
Blackline Masters
Grab and Count Stage 2 Recording Sheet

Narrative
Each student grabs a handful of ones cubes and puts them together with their partner’s. They estimate how many cubes there are and then count the cubes. Students record their estimate and the actual number of cubes on the recording sheet.
Variation:
Students can count their own group of cubes first and record an equation to represent the total number of cubes.
Additional Information
Each group of 2 needs around 80 ones cubes from the base-ten block set.


aligns: no