Free summary · Grade 6 Maths

Volume

Counting cubes and volume = length × breadth × height. Read one part at a time and tap “I know this”. Then test yourself in the quiz.

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Volume is the space inside a 3D object. Count cubes, or use a formula.

Rule

Volume of a rectangular prism = length × breadth × height: 4 cm × 3 cm × 2 cm = 24 cm³.

Volume units are cubic: cm³, m³.
1 cm³ holds exactly 1 ml of water.
Volume of a cube = s × s × s = s³.
The surface area is the total area of all the faces. A 4 × 2 × 1 prism has two faces of 4 × 2 = 8, two of 4 × 1 = 4 and two of 2 × 1 = 2, so 2 × (8 + 4 + 2) = 28 cm². A 2 × 2 × 2 cube has 6 faces of 4 cm²: 24 cm².

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Volume and surface area

Volume = length × breadth × height, because each layer has length × breadth cubes, and there are as many layers as the height.

Prism	Volume	Surface area
2 × 2 × 2	8 cm³	24 cm²
4 × 2 × 1	8 cm³	28 cm²

Rule

The same volume can have a different surface area: the cube has the least.

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Remember this: your summary

Write these points in your book. Read them again the night before the test.

Memory trick

Length, breadth, height: three measures, the 3 in cm³.

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