Cogito
Grade 1 Math · Chapter 7 · Lesson 3
Multiples of Ten
See that 10, 20, 30, and 40 have no ones at all.
10 problems · about 9 minutes · 1.NBT.B.2.c
What this lesson teaches
The child recognizes 10, 20, 30, and 40 as one, two, three, and four tens with zero ones.
- 10, 20, 30, and 40 are made of whole tens.
- They have zero ones.
- The 0 means no ones, not nothing.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
4 problemsReview — Tens and Ones on a Mat: How many tens are in 31?
Answer 3
Why 31 is 3 tens and 1 one.
Review — Counting Beyond 20: What comes right after 20?
Answer 21
Why After 20 comes 21.
Review — Asking Questions About Data: 5 apples and 2 stars. How many in all?
Answer 7
Why 5 + 2 = 7.
Review — Sorting and Showing Data: A graph shows 4 apples and 6 stars. How many in all?
Answer 10
Why 4 + 6 = 10.
Warm Up
Straightforward practice. Get the method working first.
3 problemsThree tens is which number?
Answer 30
Why Three tens is 30.
What does the 0 in 20 mean?
Answer There are no ones.
Why 20 is two tens and no ones.
How many tens are in 40?
Answer 4
Why Count the rods.
Build It Up
The same ideas with more to keep track of.
1 problemTwo tens is which number?
Answer 20
Why 10 and 10 more.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsHow many ones are in 30?
Answer 0
Why Look for loose cubes.
Egg Boxes: Each box holds ten eggs. Leo has 3 full boxes. How many eggs?
Answer 30 eggs
Why Three tens is 30.