How to see it
Simplifying a ratio is like simplifying a fraction. Divide both sides by the biggest number that goes into both. But first, both sides need the same units. You cannot compare centimetres to metres.
A worked example
Two metres is 200 centimetres. 50 to 200. Divide both by 50. 1 to 4. Three parts works the same: 12 to 18 to 30, divide by 6, 2 to 3 to 5.
The common mistake: not converting units first
The trap is dividing 50 by 2 and getting 25 to 1. The numbers are not in the same units, so the answer is meaningless. Convert, then simplify.
Try one
45 pence to £1.80.
- A1 : 4
- B45 : 1.80
- C1 : 40
- D9 : 36
Show the answerHide the answer
Right: A, 1 : 4
£1.80 is 180 pence, divide both by 45. D is correct but not simplest.