ShapesWhat each page gives you
Every shape has a labelled figure, so that there is no doubt which length each letter stands for. Under it are the formulas, a list of the shape's properties, and a plain account of why the formulas are true: a triangle is half a parallelogram, a cone is a third of a cylinder. Then comes a worked example set out line by line, the mistakes that cost marks, where the shape turns up in daily life, and questions with answers.
The calculator covers all the shapes. It lets you choose π as 22/7, 3.14 or the calculator value, and shows the formula and the numbers put into it.
Guides
- Area and perimeter: what each measures and why they are not linked.
- Surface area and volume: CSA, TSA, capacity.
- Units of area and volume: cm² to m², litres, hectares.
- Pythagoras' theorem.
- What is π, and 22/7 against 3.14.
- Polygons and their angles.
- Types of triangles and quadrilaterals.
- Faces, edges and vertices of solids.
- Mensuration word problems, solved.
How to learn mensuration
Do not start by memorising the formula sheet. Start with the square and the rectangle, where area can be counted in unit squares, and see every other formula grow out of them. Draw the figure for every question and write the measurements on it. Decide whether the question is about an edge, a covering or a filling before you choose a formula. And write the unit after every answer.
Common questions
What is the difference between area and perimeter?
Perimeter is the length of the boundary of a flat shape, measured in units such as cm or m. Area is the surface inside it, measured in square units such as cm² or m².
What is the difference between surface area and volume?
Surface area is the total area of the outside of a solid, in square units. Volume is the space it fills, in cubic units.
Should I use 22/7 or 3.14 for π?
Use the value your question gives. If it gives none, 22/7 is usual in Indian school books, especially when the radius is a multiple of 7.
How many litres is one cubic metre?
One cubic metre is 1000 litres. One litre is 1000 cubic centimetres.
More maths from our family: Tables, Factors, Numbers and printable area and perimeter worksheets.