Areas and Perimeters
Perimeter and area formulas for the plane figures that appear in bank exams: rectangle, square, parallelogram, rhombus, trapezium, triangle and circle, with the unit traps and the reverse questions that go with them.
What you will be able to do
- State the area and perimeter formula for each standard plane figure from memory.
- Choose the right formula from the measurements a question actually gives.
- Use pi as 22/7 or 3.14159 consistently and keep length units matched.
- Work a reverse question, recovering a side or radius from a given area or perimeter.
What is inside this lesson
- 1What this topic covers
- 2Quadrilaterals
- 3Triangles
- 4Circle, sector and ring
- 5Choosing the formula and matching units
- 6Worked example
- 7Common mistakes
- 8Quick revision
- 9Practice
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What this topic covers
Mensuration is the arithmetic of measurement: given a few lengths, find a perimeter (the distance round the boundary, a length) or an area (the space enclosed, a length squared).
Bank exams keep to a fixed set of plane figures — rectangle, square, parallelogram, rhombus, trapezium, triangle and circle — and reuse the same three question shapes: compute the area or perimeter directly; work backwards from a given area or perimeter to a side; or combine a figure with a cost or a count. Learn each formula so well that reading the measurements tells you which one to use.
Unless a question says otherwise, this topic takes pi as 22/7 when the numbers are chosen to cancel with 7, and 3.14159 otherwise.
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