#8
Top 50 Mistake
Moving the decimal point the wrong way
"The Backwards Shift"
The Mistake in Action
Convert 0.35 to a percentage.
Wrong: $0.35 \div 100 = 0.0035\%$
Why It Happens
Students remember "something with 100" but forget whether to multiply or divide. They may think "percentages are smaller numbers" and divide instead of multiply.
The Fix
Remember: Percentages are the "big" version.
- To make a number look bigger (decimal → percentage): multiply by 100
- To make a number look smaller (percentage → decimal): divide by 100
Check with a value you know: $0.5 = 50\%$. Did 0.5 get bigger or smaller to become 50? It got bigger, so we multiplied.
Spot the Mistake
Can you identify where this student went wrong?
Convert 0.35 to a percentage
$0.35 \div 100$
$= 0.0035\%$
Click on the line that contains the error.
Related Topics
Learn more about the underlying maths: