Cogito
Grade 1 Math · Chapter 3 · Lesson 1
How Many More To Make It?
Find the part that is missing.
10 problems · about 11 minutes · 1.OA.B.4, 1.OA.A.1
What this lesson teaches
The child solves add-to-with-change-unknown stories with addition, and sees the same situation written as a subtraction.
- A missing part is a kind of subtraction.
- 4 + ? = 7 asks the same thing as 7 − 4.
- Count up from the part you already have.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
5 problemsReview — Facts to Ten: 7 + 3 = ?
Answer 10
Why 7 + 3 = 10.
Review — Doubles and One More: 3 + 4 = ?
Answer 7
Why 3 + 3 = 6, and one more is 7.
Review — Doubles: 4 + 4 = ?
Answer 8
Why 4 + 4 = 8.
Review — Finding the Missing Part: 5 + ? = 9
Answer 4
Why 5 + 4 = 9.
Review — What Does Equals Mean?: What does the equals sign mean?
Answer Both sides are the same amount.
Why Equals means the same amount as. That is why 9 = 6 + 3 works too.
Warm Up
Straightforward practice. Get the method working first.
3 problems3 + ? = 7
Answer 4
Why 3 + 4 = 7.
5 + ? = 10
Answer 5
Why 5 + 5 = 10.
6 + ? = 9
Answer 3
Why Count up from 6 to 9.
Build It Up
The same ideas with more to keep track of.
1 problem2 + ? = 8
Answer 6
Why Count up from 2 to 8.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
1 problemCollecting Shells: Ben has 5 shells. He wants 9. How many more does he need?
Answer 4 shells
Why 5 + 4 = 9, so he needs 4 more.