Cogito
Grade 1 Math · Chapter 3 · Lesson 2
Counting Up To Subtract
Hop from the part to the whole and count the hops.
10 problems · about 11 minutes · 1.OA.B.4, 1.OA.C.5
What this lesson teaches
The child finds an unknown part by counting up on a number path, answering with the number of hops rather than the landing square.
- You can subtract by counting up.
- Start at the part and hop to the whole.
- The answer is the number of hops.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
5 problemsReview — How Many More To Make It?: 3 + ? = 7
Answer 4
Why 3 + 4 = 7.
Review — 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.
Warm Up
Straightforward practice. Get the method working first.
3 problems9 − 7 = ?
Answer 2
Why Two hops, so the answer is 2.
7 − 4 = ?
Answer 3
Why Three hops, so the answer is 3.
8 − 5 = ?
Answer 3
Why Hop from 5 up to 8.
Build It Up
The same ideas with more to keep track of.
1 problem10 − 7 = ?
Answer 3
Why Hop from 7 up to 10.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
1 problemClimbing Stairs: Mia is on step 4. The top is step 10. How many more steps must she climb?
Answer 6 steps
Why 4 + 6 = 10, so she has 6 to climb.