#27
Top 50 Mistake
Thinking percentage means out of 100 literally
"The Literal Hundred"
The Mistake in Action
Write $\frac{7}{20}$ as a percentage.
Wrong: "It's not out of 100, so I can't convert it"
Why It Happens
Students learn that "percent means out of 100" and interpret this too literally.
The Fix
"Out of 100" means we need to scale the fraction so the denominator becomes 100.
Method 1: Find an equivalent fraction with denominator 100 $$\frac{7}{20} = \frac{7 \times 5}{20 \times 5} = \frac{35}{100} = 35\%$$
Method 2: Divide then multiply by 100 $$\frac{7}{20} = 7 \div 20 = 0.35 \rightarrow 35\%$$
Spot the Mistake
Can you identify where this student went wrong?
Write $\frac{7}{20}$ as a percentage
The denominator is 20, not 100
So this cannot be written as a percentage
Click on the line that contains the error.
Related Topics
Learn more about the underlying maths: