Fractions, Shapes and Data
Primary 3 · Mathematics
Fractions, Shapes and Data
Lesson 1 of 3
13 min
Let's begin
It is evening at Uwase's home. Her mother brings one warm chapati to the table. But two hungry children are waiting: Uwase and her brother Gatete.
One chapati, two children. How do you share it so that nobody complains? Today you will learn the maths that is hiding inside that cut.
Uwase's mother cuts the chapati straight down the middle. Now there are 2 pieces, and both pieces are exactly the same size.
Each piece is called one half. We write it like this:
12
Look carefully at those two numbers.
Now here is something to watch. Suppose Gatete grabs the chapati and tears it into 2 pieces: one huge piece and one tiny piece. There are still 2 pieces... but they are not halves. Halves must be the same size. If the parts are not equal, the pieces get no fraction name at all.
The next evening, three children sit at the table. Mother cuts the chapati into 3 equal pieces.
Each piece is one third. We write 13.
Bottom number 3: cut into 3 equal parts. Top number 1: we are taking 1 piece.
On Sunday, four children come. Mother cuts the chapati into 4 equal pieces.
Each piece is one quarter. We write 14.
Keza's chapati is cut into 4 equal quarters. She eats 3 of them.
The bottom number is still 4, because that is how many equal parts there are. The top number is now 3, because that is how many she ate.
So Keza ate 34 of the chapati. We say three quarters.
How much is still on the plate? Only 1 piece out of the 4. So 14 is left.
Fractions do not only cut up one thing. They also share out a group of things. The rule does not change: make equal groups.
Worked example
Mugisha has 12 beans. He wants to give his sister 13 of them. How many beans is that?
So 13 of 12 = 4. His sister gets 4 beans.
One more. What is 12 of 10 Frw?
Bottom number 2, so make 2 equal groups: 5 and 5. Take 1 group. So 12 of 10 = 5. It is 5 Frw.
This one catches a lot of children, so read it slowly. Imagine three chapatis, all exactly the same size.
The chapati never grew. It was only shared between more and more people, so each person got less.
That means:
12 is bigger than 13, and 13 is bigger than 14.
So a bigger bottom number gives you a smaller piece. It feels backwards at first! Just picture the table: more friends sitting down means less chapati for you.
Tip
The bottom number counts the cuts. The top number counts what you take. In 34, the 4 says the whole thing was cut into 4 equal parts and the 3 says take 3 of them. And never forget the chapati rule: more people at the table, smaller piece for each one.
Do each one on your own first, then tap Show answer to check.
A chapati is cut into 4 equal parts. Umutoni eats 1 part. What fraction did she eat?
Answer: 14. There are 4 equal parts (bottom number 4) and she took 1 of them (top number 1).
A cake is cut into 3 equal parts. Ishimwe eats 2 of them. What fraction did he eat?
Answer: 23. Bottom number 3 for the three equal parts, top number 2 for the two he ate.
What is 12 of 8 mangoes?
Answer: 4 mangoes. Make 2 equal groups: 4 and 4. Take one group.
What is 14 of 12 pencils?
Answer: 3 pencils. Make 4 equal groups: 3, 3, 3 and 3. Take one group.
Keza and Mutesi each have the same size chapati. Keza eats 12 of hers. Mutesi eats 13 of hers. Who ate more?
Answer: Keza. A half is a bigger piece than a third, because her chapati was cut into fewer pieces.
What you learned today
Quick check
A chapati is cut into 4 equal parts. Keza eats 3 parts. What fraction is left?
