2nd Grade Mathematics Lesson
Farmer Dan's Egg Carton Snap: Make a 10 Mental Math Superpower
Shared by A STEM Educator
2nd GradeBuilding Thinking Classrooms (BTC)CCSS.MATH.CONTENT.2.OA.B.2, CCSS.MATH.CONTENT.1.OA.C.650 min
Learning Objective
Students will decompose the second addend to complete a group of ten, then add remaining ones, fluently applying the Make-a-10 strategy to addition facts within 20 and extending it to near-tens within 50.
Lesson Overview
Students move from inefficient counting-on strategies to flexible Make-a-10 decomposition by reorganizing eggs into full cartons of 10, progressing from 9+facts through 7+facts and into near-tens in the 20s and 40s.
Materials
- Vertical non-permanent surfaces (whiteboards, windows, chart paper)
- Dry-erase markers (one per group)
- Two-color counters (red/blue) per group
- Double ten-frame mats (laminated or drawn on board)
- Anchor chart paper and markers
- Exit slip half-sheets
- Farmer Dan egg carton visual (projected or printed)
Scaffolded Task Progression
1Task 1
Farmer Dan's Egg Carton Problem (Teacher-Anchored Task)
An egg carton holds 10 eggs. Farmer Dan has 8 eggs in one carton and 6 eggs in another. He wants to pack as many full 10-cartons as possible before selling them.
Draw the cartons on your board or use your counters: How can Farmer Dan reorganize his eggs so he has one full carton of 10 and a leftover pile?
Show: (1) the starting picture, (2) the move you made, and (3) the number sentence.
An egg carton holds 10 eggs. Farmer Dan has 8 eggs in one carton and 6 eggs in another. He wants to pack as many full 10-cartons as possible before selling them.
Draw the cartons on your board or use your counters: How can Farmer Dan reorganize his eggs so he has one full carton of 10 and a leftover pile?
Show: (1) the starting picture, (2) the move you made, and (3) the number sentence.
2Task 2
Slice 1 — 9-Plus Strategy
Farmer Dan now has 9 eggs in one box and 7 eggs in another.
Show on your board how becomes .
Write BOTH number sentences:
- Starting fact:
- Bridge fact:
How many eggs does Farmer Dan have in all?
Farmer Dan now has 9 eggs in one box and 7 eggs in another.
Show on your board how becomes .
Write BOTH number sentences:
- Starting fact:
- Bridge fact:
How many eggs does Farmer Dan have in all?
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