#31
Top 50 Mistake
Adding highest and lowest instead of subtracting
"The Range Reversal"
The Mistake in Action
Find the range of: 3, 7, 12, 4, 9
Student writes: "Range = 12 + 3 = 15"
Why It Happens
Students remember the range involves the highest and lowest values but use addition instead of subtraction. Sometimes they've confused it with another formula.
The Fix
Range is about the spread — how far apart the data stretches.
$$\text{Range} = \text{Highest} - \text{Lowest}$$
Range = 12 − 3 = 9
Think of it this way: If you stretch a rubber band from the lowest to highest value, how long is it? That's a "difference" — subtraction!
Spot the Mistake
Can you identify where this student went wrong?
Highest value = 12
Lowest value = 3
Range = 12 + 3 = 15
Click on the line that contains the error.
Related Topics
Learn more about the underlying maths: