Cogito
Grade 1 Math · Chapter 2 · Lesson 4
Adding in Any Order
Swap the parts and the total stays the same.
10 problems · about 12 minutes · 1.OA.B.3, 1.OA.C.6
What this lesson teaches
The child discovers that the order of the addends does not change the total, and uses it to start counting on from the larger number.
- Swapping the parts does not change the total.
- Start with the bigger number.
- Then you have fewer hops to count.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
5 problemsReview — Counting On With Pictures: Start at 9. Count on 1. Where do you land?
Answer 10
Why 9 + 1 = 10.
Review — Counting On: 8 + 2 = ?
Answer 10
Why 8 + 2 = 10.
Review — Putting Groups Together: What is 4 + 2?
Answer 6
Why 4 + 2 = 6.
Review — How Many Do You See?: How many dots?
Answer 4
Why A dice four is worth knowing by sight.
Review — One More, One Less: What is one more than 4?
Answer 5
Why One more than 4 is 5.
Warm Up
Straightforward practice. Get the method working first.
3 problems3 + 5 = 8. So what is 5 + 3?
Answer 8
Why Swapping the parts never changes the whole.
Which is quicker to count on?
Answer Start at 8 and count on 2.
Why Both give 10, but starting at 8 needs only two hops.
1 + 8 = ?
Answer 9
Why Think 8 + 1 instead.
Build It Up
The same ideas with more to keep track of.
1 problem2 + 6 = ?
Answer 8
Why Think 6 + 2 instead.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
1 problemSharing Grapes: Mia eats 3 grapes and Ben eats 6. How many grapes did they eat in all?
Answer 9 grapes
Why 6 + 3 = 9, which is the same as 3 + 6.