Cogito
Grade 1 Math · Chapter 7 · Lesson 2
Tens and Ones on a Mat
Show any number to 40 as tens and ones.
10 problems · about 12 minutes · 1.NBT.B.2
What this lesson teaches
The child represents a two-digit number to 40 as a number of tens and a number of ones.
- A two-digit number is made of tens and ones.
- The first digit tells how many tens.
- The second digit tells how many ones.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
4 problemsReview — 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.
Review — How Much Longer?: A 9-cube stick and a 4-cube stick. How much longer is the first?
Answer 5
Why 9 − 4 = 5.
Warm Up
Straightforward practice. Get the method working first.
3 problemsHow many tens are in 31?
Answer 3
Why 31 is 3 tens and 1 one.
2 tens and 5 ones is which number?
Answer 25
Why 20 and 5 more is 25.
How many tens are in 27?
Answer 2
Why Count the rods.
Build It Up
The same ideas with more to keep track of.
1 problemHow many ones are in 27?
Answer 7
Why Count the loose cubes.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problems3 tens and 8 ones is which number?
Answer 38
Why Say the tens, then the ones.
Packing Pencils: Pencils come in boxes of ten. 3 boxes and 2 loose. How many?
Answer 32 pencils
Why 3 tens and 2 ones is 32.