Cogito
Grade 1 Math · Chapter 4 · Lesson 6
One More, One Less to Twenty
Keep going past ten, including the tricky bit at 19.
10 problems · about 11 minutes · 1.NBT.A.1
What this lesson teaches
The child finds one more and one less than any number to 20, including across the 19 to 20 boundary.
- One more is the next number, even past ten.
- One less is the number before.
- After 19 comes 20.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
4 problemsReview — Breaking Teen Numbers Apart: 12 is 10 and what?
Answer 2
Why 12 is 10 and 2.
Review — Writing Teen Numbers: In 16, how many ones are there?
Answer 6
Why 16 is one ten and 6 ones.
Review — Saying It the Ten Way: Ten five is which number?
Answer 15
Why Ten five is fifteen.
Review — Ten and Some More: 10 + 2 = ?
Answer 12
Why 10 + 2 = 12.
Warm Up
Straightforward practice. Get the method working first.
3 problemsOne more than 11?
Answer 12
Why One more than 11 is 12.
One less than 20?
Answer 19
Why One less than 20 is 19.
One more than 13?
Answer 14
Why Next after 13.
Build It Up
The same ideas with more to keep track of.
1 problemOne less than 16?
Answer 15
Why Before 16.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsOne more than 19?
Answer 20
Why The tricky one.
Marbles: Leo has 17 marbles. He finds 1 more. How many now?
Answer 18 marbles
Why One more than 17 is 18.