#50
Top 50 Mistake
Using the wrong inequality sign for upper bound H
"The Inequality Slip"
The Mistake in Action
A length is 4.7 m to 1 decimal place. Write the error interval.
Wrong: $4.65 \leq x \leq 4.75$
Why It Happens
Students use ≤ for both bounds, not realising the upper bound itself would round UP, not to the given value.
The Fix
The upper bound uses $<$ (strict inequality) because the actual value must be less than the upper bound.
$4.75$ would round to $4.8$, not $4.7$.
Correct error interval: $4.65 \leq x < 4.75$
Remember:
- Lower bound: $\leq$ (can equal this value)
- Upper bound: $<$ (must be less than this value)
Spot the Mistake
Can you identify where this student went wrong?
$4.65 \leq x$
$\leq 4.75$
Click on the line that contains the error.
Related Topics
Learn more about the underlying maths: