Cogito
Grade 1 Math · Chapter 3 · Lesson 8
Subtracting From Ten
Your partners to ten work backwards too.
10 problems · about 11 minutes · 1.OA.C.6, 1.OA.B.4
What this lesson teaches
The child relates every subtraction from 10 to its partner-to-ten decomposition.
- Partners to ten work backwards.
- If 6 and 4 make ten, then 10 − 6 = 4.
- These are worth knowing by heart.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
4 problemsReview — Taking Nothing and Taking All: 10 − 10 = ?
Answer 0
Why Take all away and none are left.
Review — Fact Families: You know 4 + 5 = 9. What is 9 − 4?
Answer 5
Why Same fact, read the other way.
Review — What Changed?: 9 − ? = 6
Answer 3
Why 9 − 3 = 6.
Review — The Hidden Part: Whole 9, one part 4. What is the other part?
Answer 5
Why 4 + 5 = 9.
Warm Up
Straightforward practice. Get the method working first.
3 problems10 − 6 = ?
Answer 4
Why 10 − 6 = 4.
10 − 8 = ?
Answer 2
Why 10 − 8 = 2.
10 − 2 = ?
Answer 8
Why 2 and 8 are partners.
Build It Up
The same ideas with more to keep track of.
1 problem10 − 5 = ?
Answer 5
Why 5 and 5 are partners.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problems9 − 4 = ?
Answer 5
Why Count up from 4 to 9.
Egg Box Again: A box holds 10 eggs. 4 are used. How many are left?
Answer 6 eggs
Why 10 − 4 = 6, because 4 and 6 make ten.