Cogito
Grade 5 Math · Chapter 7 · Lesson 1
Dividing a Whole Number by a Unit Fraction
How many small pieces fit?
10 problems · about 16 minutes · 5.NF.B.7
What this lesson teaches
The child divides a whole number by a unit fraction and explains why the answer grows.
- Dividing by a unit fraction counts how many fit.
- The answer is bigger than the number you started with.
- The smaller the piece, the more of them fit.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
2 problemsReview — Multiplying Mixed Numbers: 1 1/2 × 6. What is the answer?
Answer 9
Why 9.
Review — Area with Fractional Sides: 1/2 by 2/5. What is the bottom number of the area?
Answer 10
Why 2/10, which is 1/5.
Warm Up
Straightforward practice. Get the method working first.
4 problems6 ÷ 1/3 = ?
Answer 18
Why 18 thirds fit into 6.
What does 4 ÷ 1/3 ask?
Answer How many thirds fit into 4.
Why Division counts how many fit.
3 ÷ 1/4 = ?
Answer 12
Why 4 in each whole.
7 ÷ 1/2 = ?
Answer 14
Why 2 in each whole.
Build It Up
The same ideas with more to keep track of.
2 problems4 ÷ 1/5 = ?
Answer 20
Why 5 in each whole.
Does dividing by a unit fraction make the answer bigger?
Answer Yes. Small pieces fit many times.
Why Count the halves in 7.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsThe Ribbons: 6 metres cut into pieces of 1/2 metre. How many pieces?
Answer 12 pieces
Why 12 pieces.
The Servings: 5 pizzas cut into quarters. How many quarters?
Answer 20 quarters
Why 20 quarters.