Cogito
Grade 4 Math · Chapter 2 · Lesson 2
Multiplying by 10, 100, and 1,000
Counting in bigger units.
10 problems · about 13 minutes · 4.NBT.B.5
What this lesson teaches
The child multiplies one-digit numbers by 10, 100, and 1,000 and by multiples of them.
- Multiplying by 100 means counting hundreds.
- The zeros appear because of the unit, not by a rule.
- Multiples work the same way: 6 × 300 is 18 hundreds.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
2 problemsReview — Multiplication as Comparison: 4 times as many as 12 is?
Answer 48
Why 4 × 12 = 48.
Review — Subtracting Multi-Digit Numbers: 6,004 − 2,738 = ?
Answer 3266
Why 6,004 − 2,738 = 3,266.
Warm Up
Straightforward practice. Get the method working first.
4 problems8 × 700 = ?
Answer 5600
Why 8 × 7 = 56, so 8 × 700 = 5,600.
Why does 6 × 100 end in two zeros?
Answer Because the answer is a number of hundreds.
Why The unit is a hundred, so the answer is written in hundreds.
7 × 100 = ?
Answer 700
Why 7 hundreds.
4 × 600 = ?
Answer 2400
Why 24 hundreds.
Build It Up
The same ideas with more to keep track of.
2 problems9 × 50 = ?
Answer 450
Why 45 tens.
6 × 2,000 = ?
Answer 12000
Why 12 thousands.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsThe Crates: 8 crates each hold 200 apples. How many apples?
Answer 1600 apples
Why 16 hundreds is 1,600.
The Boxes: 5 boxes each hold 3,000 sheets. How many sheets?
Answer 15000 sheets
Why 15 thousands is 15,000.