Lesson 3 of 15
The same comparison in bigger numbers
Show on a big screenSquash is a fruit syrup. A small jug uses 3 spoons of squash to 2 of water. A big jug uses 12 to 8. Do they taste the same?
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Step 1 of 3
- Ratio 3 : 2, drawn as two bars.
- Multiply both parts by 4: 12 : 8.
- Both divide to 1.5 — same comparison.
The rule
Yes. 12 : 8 is 3 : 2 with both parts multiplied by 4.
Ratios that make the same comparison are equivalent ratios. Multiply both parts by the same number, not zero. The comparison does not change.
- Take 5 : 4. Multiply both parts by 3: 5 × 3 = 15 and 4 × 3 = 12. That gives 15 : 12.
- To find ? in 15 : 20 = ? : 80, notice that 20 × 4 = 80. Multiply 15 by 4 too: 15 × 4 = 60.
Watch out!
Adding the same number to both parts usually changes the ratio. Adding 4 to 3 : 2 gives 7 : 6. But 3 ÷ 2 = 1.5, and 7 ÷ 6 is about 1.17.
Try the lab to finish this lesson.