standard_description: Give an informal argument for the formulas for the circumference of a circle, area of a circle, volume of a cylinder, pyramid, and cone. Use dissection arguments, Cavalieri’s principle, and informal limit arguments.
problem_activity: Stage 2: Make 10
Required Preparation
Materials to Gather
10-frames
Connecting cubes or counters
Number cards 0–10
Materials to Copy
Blackline Masters
Find the Pair Stage 2 Recording Sheet

Narrative
Partner A asks their partner for a number that would make 10 when added to the number on one of their cards. If Partner B has the card, they give it to Partner A. If not, Partner A chooses a new card. When students make the target number 10, they put down those two cards and write an equation to represent the combination. Students continue playing until one player runs out of cards. The player with the most pairs wins.


aligns: no