How to see it
Cut each part into more pieces and the amount does not change. Multiply the top and bottom by the same number and you make an equivalent fraction. Divide both by the same number and you simplify. Whatever you do to the top, do to the bottom.
A worked example
Simplify 18 over 24. What goes into both? Six goes into both. 18 divided by 6 is 3. 24 divided by 6 is 4. Three quarters. Check: can 3 and 4 be divided by anything else? No. Done.
The common mistake: adding the same number top and bottom
The trap is adding. Three quarters, add 2 to both, five sixths. That feels the same, but five sixths is bigger. It must be multiply or divide, never add or subtract.
Try one
Simplify 28 over 42.
- A14/20
- B4/7
- C2/3
- D7/10
Show the answerHide the answer
Right: C, 2/3
Both numbers divide by 14, the biggest common factor, so one step takes you all the way.