What is a ratio in simple terms?

A ratio compares two amounts, telling you how many of one thing there are for every amount of another. It is written like a : b and said as "a to b", for example 3 : 2 meaning 3 apples for every 2 oranges.

Does the order of the numbers in a ratio matter?

Yes. The order must match the order of the things being compared. The ratio of 5 girls to 4 boys is 5 : 4, while 4 : 5 would describe boys to girls — a different meaning.

How can two different-looking ratios be the same?

A ratio stays the same as long as both sides are multiplied by the same number. So 2 : 1, 4 : 2 and 6 : 3 are all equivalent because each side grew by the same factor.

Where are ratios used in everyday life?

Ratios appear when mixing drinks or recipes (such as 1 cup of syrup to 3 cups of water), in map scales, in sharing things fairly, and in comparing quantities like speed or price per item.

When do Singapore primary students learn ratio?

Ratio is formally introduced in the Primary 5 Mathematics syllabus and extended in Primary 6, but the basic idea of comparing two groups can be understood much earlier through counting and pictures.

What Is a Ratio?

Math Interactive lesson Free to play

A ratio is a way to compare two amounts, showing how many of one thing there are for every amount of another. It is written with a colon, such as 2 : 1, and read aloud as "2 to 1" — meaning two of the first item for every one of the second. For example, if a tank has 2 dogs for every 1 cat, the ratio of dogs to cats is 2 : 1.

Ratios matter because they describe relationships rather than exact totals, which makes them useful far beyond the classroom. They appear when mixing drinks (1 cup of syrup to 3 cups of water), in recipes, in maps and scale drawings, and later in topics like proportion, percentage, and rate.

The key ideas a learner grasps are: order matters, so 2 : 1 is not the same as 1 : 2; both numbers must refer to clearly counted groups; and a ratio stays the same when both sides grow by the same multiple, so 2 : 1, 4 : 2 and 6 : 3 all describe the identical relationship. In Singapore's primary syllabus, ratio is formally introduced in Primary 5 Mathematics and built on in Primary 6.

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What this Spark covers

Welcome

What Is a Ratio? 🍎🍊 A ratio is a way to compare how many of one thing there are next to another thing. 🐶🐶 vs 🐱 2 dogs for every 1 cat. 2 : 1 We say this out loud as “two to one”. Tap Next and let's learn how ratios work, step by step! 👉
Compare two groups

Step 1: Compare two groups A ratio compares two amounts. Here are some apples and oranges. Count them! 🍎🍎🍎 🍊🍊 3 apples and 2 oranges. We write the ratio of apples to oranges as: 3 : 2 The little dots : mean “to”. Order matters — apples first, oranges second. 👉 Next, you'll try counting one yourself.
Tap and count

Step 2: Tap to count 🖐️ Here is a row of stars and moons. Tap each shape to count it, then tell me the ratio of stars to moons. Stars tapped: 0 · Moons tapped: 0 What is the ratio of ⭐ stars : 🌙 moons? 2 : 4 4 : 2 4 : 4
Build a ratio

Step 3: Build a ratio 🧺 Let's make the ratio 3 : 1 of fish to bones. Drag the right number of each into the baskets. 🐟 Fish (need 3) 🦴 Bones (need 1) 🐟 🐟 🐟 🐟 🦴 🦴 Tip on a tablet: tap a token, then tap a basket to drop it.
Ratios scale up

Step 4: Ratios can grow 📈 Magic of ratios: 2 : 1 can become 4 : 2 or 6 : 3. As long as both sides grow the same number of times, it's the same ratio! 2 : 1 ➕ Double the recipe ↺ Reset Every blue circle still has exactly one orange friend. 🎉
Real life ratios

Step 5: Ratios in real life 🥤 To make orange squash, you mix 1 cup of syrup with 3 cups of water. That's a ratio of 1 : 3. 🧡 : 💧💧💧 If a friend wants to use 2 cups of syrup, how much water keeps the same tasty ratio? 3 cups 6 cups 2 cups Hint: syrup doubled (1 → 2), so water must double too.
Quick quiz

Step 6: Be the ratio expert 🏆 A classroom has 5 girls and 4 boys. What is the ratio of girls to boys? 👧👧👧👧👧 👦👦👦👦 4 : 5 5 : 4 9 : 5 Remember: write them in the order asked — girls first!
You did it!

🎉 You're a Ratio Star! Let's recap what a ratio is: 🔹 A ratio compares two amounts, written like a : b and said as “a to b”. 🔹 Order matters — write them in the order you're asked. 🔹 A ratio stays the same when both sides grow the same number of times (2 : 1 = 4 : 2 = 6 : 3). 🔹 Ratios are everywhere — drinks, recipes, teams and games! 🥤⚽ Well done, ratio detective! Tap Start again any time to play once more. ✨

Frequently asked questions

What is a ratio in simple terms?: A ratio compares two amounts, telling you how many of one thing there are for every amount of another. It is written like a : b and said as "a to b", for example 3 : 2 meaning 3 apples for every 2 oranges.
Does the order of the numbers in a ratio matter?: Yes. The order must match the order of the things being compared. The ratio of 5 girls to 4 boys is 5 : 4, while 4 : 5 would describe boys to girls — a different meaning.
How can two different-looking ratios be the same?: A ratio stays the same as long as both sides are multiplied by the same number. So 2 : 1, 4 : 2 and 6 : 3 are all equivalent because each side grew by the same factor.
Where are ratios used in everyday life?: Ratios appear when mixing drinks or recipes (such as 1 cup of syrup to 3 cups of water), in map scales, in sharing things fairly, and in comparing quantities like speed or price per item.
When do Singapore primary students learn ratio?: Ratio is formally introduced in the Primary 5 Mathematics syllabus and extended in Primary 6, but the basic idea of comparing two groups can be understood much earlier through counting and pictures.

What Is a Ratio?

What this Spark covers

Frequently asked questions

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