Cogito
Grade 5 Math · Chapter 4 · Lesson 4
Dividing Decimals
How many of these fit into that?
10 problems · about 16 minutes · 5.NBT.B.7
What this lesson teaches
The child divides decimals by whole numbers and explains the size of the answer.
- Read the decimal as a count, then divide the count.
- Dividing by less than 1 makes the answer bigger.
- Division asks how many fit, not how much is left.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
2 problemsReview — When Multiplying Makes Things Smaller: What is 0.25 × 40?
Answer 10
Why 10.
Review — Multiplying a Decimal by a Whole Number: 9 × 0.3, in tenths?
Answer 27
Why 27 tenths, which is 2.7.
Warm Up
Straightforward practice. Get the method working first.
4 problemsHow many halves fit into 9?
Answer 18
Why 18 halves.
Why does dividing by less than 1 make the answer bigger?
Answer Small pieces fit in many times.
Why Division counts how many fit, and small pieces fit often.
0.6 ÷ 2, in tenths?
Answer 3
Why 6 tenths among 2.
0.75 ÷ 5, in hundredths?
Answer 15
Why 75 hundredths among 5.
Build It Up
The same ideas with more to keep track of.
2 problemsHow many quarters fit into 5?
Answer 20
Why 4 in each whole.
Dividing by 0.5. Does the answer grow or shrink?
Answer It grows.
Why Small pieces fit in many times.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsThe Share: 0.9 shared among 3. How many tenths each?
Answer 3 tenths
Why 3 tenths each, which is 0.3.
The Halves: How many halves fit into 6?
Answer 12 halves
Why 12 halves.