Cogito
Grade 2 Math · Chapter 3 · Lesson 1
A New Unit: The Hundred
Ten tens bundle into one hundred.
10 problems · about 11 minutes · 2.NBT.A.1
What this lesson teaches
The child recognizes a hundred as ten tens and as one new unit.
- Ten tens bundle into one hundred.
- A hundred is a new unit you can count.
- Numbers now have hundreds, tens, and ones.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
3 problemsReview — Adding and Subtracting on a Number Line: Start at 26 and jump forward 20. Where do you land?
Answer 46
Why 26 + 20 = 46.
Review — From Ruler to Number Line: How far is 13 from 0 on a number line?
Answer 13
Why 13 is 13 units from 0.
Review — Length Word Problems: A 23 cm and a 19 cm strip joined. How long in all?
Answer 42
Why 23 + 19 = 42 centimetres.
Warm Up
Straightforward practice. Get the method working first.
3 problemsHow many tens are in one hundred?
Answer 10
Why Ten tens make a hundred.
In 342, how many hundreds are there?
Answer 3
Why 342 has 3 hundreds.
How many tens make one hundred?
Answer 10
Why Count the rods in the square.
Build It Up
The same ideas with more to keep track of.
1 problemHow many ones make one hundred?
Answer 100
Why Ten tens, and each ten is ten ones.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
3 problems4 hundreds is which number?
Answer 400
Why 100, 200, 300, 400.
Boxes of Ten: A crate holds ten boxes. Each box holds ten pencils. How many pencils in a crate?
Answer 100 pencils
Why Ten tens is one hundred.
Three Crates: Leo has 3 crates of a hundred pencils each. How many pencils does he have?
Answer 300 pencils
Why Three hundreds is 300.