Cogito
Grade 1 Math · Chapter 10 · Lesson 3
Numbers to 100
Tens and ones work the same all the way to 100.
10 problems · about 12 minutes · 1.NBT.B.2
What this lesson teaches
The child represents any number to 100 as tens and ones, and recognizes 100 as ten tens.
- Every number to 100 is tens and ones.
- The first digit is the tens.
- Ten tens make 100.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
4 problemsReview — Two-Bar Tape Diagrams: Bars of 15 and 8. What is the difference?
Answer 7
Why 15 − 8 = 7.
Review — How Many More? How Many Fewer?: 10 birds and 6 cats. How many more birds?
Answer 4
Why 10 − 6 = 4.
Review — Telling Time to the Half Hour: How many minutes is half an hour?
Answer 30
Why Half an hour is 30 minutes.
Review — Telling Time to the Hour: Short hand on 4, long hand up. What hour?
Answer 4
Why It is 4 o’clock.
Warm Up
Straightforward practice. Get the method working first.
3 problemsHow many ones are in 86?
Answer 6
Why 86 is 8 tens and 6 ones.
9 tens and 2 ones is which number?
Answer 92
Why 90 and 2 more is 92.
How many tens are in 74?
Answer 7
Why The first digit.
Build It Up
The same ideas with more to keep track of.
1 problem5 tens and 9 ones is which number?
Answer 59
Why 5 tens is 50.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsHow many tens are in 100?
Answer 10
Why Count the rods.
Boxes of Crayons: Boxes hold ten crayons. 8 boxes and 4 loose. How many?
Answer 84 crayons
Why 8 tens and 4 ones is 84.