Geometry and Measurement
Perimeter is the distance around; area is the space inside. Learn the formulas for the rectangle, square, triangle and circle, sketch before you solve, and convert units first.
What it is
Plane figures are flat shapes such as rectangles, squares, triangles and circles. For each one you can measure two things:
- Perimeter: the distance around the shape (for a circle it is called the circumference). It is a length, so it uses units like m or cm.
- Area: the amount of flat space inside the shape. It counts unit squares, so it uses square units like m² or cm².
You will also convert between units, such as km to m or inches to cm.
Why it matters on the exam
The exam asks a few geometry items in every Numerical Ability part: a lot to be fenced, a floor to be tiled, a table with a round edge, or a rectangle whose sides are described in words. The formulas are short, so these are points you can secure. The usual traps are using the wrong formula (perimeter instead of area), forgetting the ½ for triangles, using the diameter as the radius, and mixing units.
At work, you use the same skills when you estimate tiles, paint, fencing, or office floor space.
- 10 m
- 25 m
- 125 m²
- 250 m²
The rest of this lesson, and every other lesson, is part of ReviewTayo.
Read moreIn the full lesson
- How to recognize it on the test
- What to look for (5 checks)
- All 7 rules and tools
- 5 worked examples, every step explained
- 7 common mistakes and how to fix them
- 3 exam techniques
- Remember: 4 key points
- Practice questions with explanations, and your progress saved
More Numerical Ability lessons
ReviewTayo has 47 lessons that follow the official scope of the exam, each with rules, worked examples, common mistakes and practice. Open one and read the first part.