A ratio compares two quantities by showing how much of one thing there is relative to another. It answers the question: "For every ___ of this, how many of that?"
Real-World Examples
A classroom has 12 boys and 8 girls. The ratio of boys to girls is 12 to 8.
A recipe calls for 2 cups of flour and 1 cup of sugar. The ratio of flour to sugar is 2 to 1.
Order Matters
The order of numbers in a ratio matters. The ratio of boys to girls (12 to 8) is not the same as the ratio of girls to boys (8 to 12). Always match the order to the words.
Think of it like reading a sentence: "boys to girls" means boys come first.
Ratios Are Everywhere
You use ratios without realizing it — mixing paint colors, following recipes, calculating speed (miles per hour), or comparing prices (cost per item). A ratio is just a structured way to describe the relationship between two numbers.
💡 Key idea: A ratio doesn't tell you the actual amounts — just the relationship. A ratio of 2 to 1 could mean 2 and 1, or 20 and 10, or 200 and 100. The relationship stays the same.
🎯 Practice Problems
1. A bag has 5 red marbles and 3 blue marbles. What is the ratio of red to blue?
A) 3 to 5
B) 5 to 3
C) 8 to 5
D) 5 to 8
2. There are 4 cats and 7 dogs. What is the ratio of dogs to cats?
A) 4 to 7
B) 7 to 4
C) 4 to 11
D) 7 to 11
3. A recipe uses 3 cups of rice and 6 cups of water. What is the ratio of rice to water?
A) 6 to 3
B) 3 to 6
C) 1 to 3
D) 3 to 9
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🎯 Bonus Practice
1. A parking lot has 20 cars and 5 trucks. What is the ratio of cars to trucks?
A) 5 to 20
B) 20 to 5
C) 25 to 20
D) 20 to 25
2. If the ratio of apples to oranges is 4 to 3, can there be 8 apples and 6 oranges?
A) No — the ratio is different
B) Yes — the relationship is the same
C) Only if there are exactly 4 and 3
D) Not enough information
3. A class has 10 boys and 15 girls. What is the ratio of girls to boys?