#15
Top 50 Mistake
Dividing numerator and denominator by different numbers
"The Unequal Split"
The Mistake in Action
Simplify $\frac{12}{18}$
Wrong: $\frac{12}{18} = \frac{12 \div 2}{18 \div 3} = \frac{6}{6} = 1$
Why It Happens
Students know they need to divide both parts but don't realise it must be by the same number.
The Fix
When simplifying a fraction, you must divide the top and bottom by the same number.
Ask yourself: "What number goes into BOTH 12 AND 18?"
$\frac{12}{18} = \frac{12 \div 6}{18 \div 6} = \frac{2}{3}$
Spot the Mistake
Can you identify where this student went wrong?
Simplify $\frac{12}{18}$
$= \frac{12 \div 2}{18 \div 3}$
$= \frac{6}{6} = 1$
Click on the line that contains the error.
Related Topics
Learn more about the underlying maths: