Cogito
Grade 3 Math · Chapter 5 · Lesson 3
Fractions as Copies of a Unit
Three quarters is three one-quarters.
10 problems · about 12 minutes · 3.NF.A.1
What this lesson teaches
The child interprets a/b as a copies of the unit fraction 1/b.
- a/b means a copies of 1/b.
- The numerator counts the pieces you have.
- Counting fractions works like counting anything else.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
3 problemsReview — Unit Fractions: Which is bigger, 1/4 or 1/6?
Answer 1/4
Why 1/4 is bigger, even though 4 is the smaller number.
Review — Equal Parts of a Whole: A shape cut into 5 equal parts. What is the denominator?
Answer 5
Why The denominator is 5.
Review — Area of Joined Shapes: A 6 by 3 part and a 4 by 2 part. Total area?
Answer 26
Why 18 + 8 = 26 square units.
Warm Up
Straightforward practice. Get the method working first.
3 problemsHow many copies of 1/8 make 5/8?
Answer 5
Why 5/8 is five copies of 1/8.
6 equal parts, 4 shaded. What fraction is shaded?
Answer 4 sixths
Why 4/6 is shaded.
How many copies of 1/4 make 3/4?
Answer 3
Why The numerator.
Build It Up
The same ideas with more to keep track of.
1 problem2 pieces out of 5 equal parts. What is the numerator?
Answer 2
Why How many you have.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
3 problems2 pieces out of 5 equal parts. What is the denominator?
Answer 5
Why How many the whole was cut into.
The Chocolate Bar: A bar has 8 equal pieces. You eat 5. What fraction did you eat?
Answer 5 eighths
Why You ate 5/8.
Counting Copies: How many copies of 1/6 make 4/6?
Answer 4
Why 4/6 is four copies of 1/6.