Lesson 5 cube numbers

Cube Numbers

1. CUBE NUMBERS ALAN S. ABERILLA

2. A cube number is the result when a number has been multiplied by itself twice. The symbol for cubed is  3 . For example, 8 is a cube number because it’s 2 x 2 x 2 (2 multiplied by itself twice); this is also written as 2 3  (“two cubed”). Another cube number is 27 because it’s 3 3  (3 x 3 x 3, or “three cubed ”). List of cube numbers up to 10 x 10 x 10 The first 10 cube numbers are: 1 = 1 x 1 x 1 or 1 3 216 = 6 x 6 x 6 or 6 3 8 = 2 x 2 x 2 or 2 3 343 = 7 x 7 x 7 or 7 3 27 = 3 x 3 x 3 or 3 3 512 = 8 x 8 x 8 or 8 3 64 = 4 x 4 x 4 or 4 3 729 = 9 x 9 x 9 or 9 3 125 = 5 x 5 x 5 or 5 3 1,000 = 10 x 10 x 10 or 10 3 The cube numbers from 1 to 100 are: 1, 8, 27, 64

3. Why are they called cube numbers? They are named cube numbers (or cubed numbers) because they can also be used to calculate the volume of a cube: since a cube has sides of the same length, width and height, you calculate its volume by multiplying the side length by itself twice (or ‘cubing’ it ). As cubes have equal sides (length, height and width), calculating the volume is simple – just “cube” (multiply by itself twice) one of its sides! For example, a cube with side length 2cm would have a volume of 8cm 3  (as 2 3  = 8). In reverse, if we knew a cube had a volume of 27cm 3 , we’d know that each side would measure 3cm (as 3 3  = 27). See the diagrams below to demonstrate these examples.

4. A cube with side length 2 units, volume 8 units i.e. 2 x 2 x 2 – we can also see there are 8 cubes. 2 . A cube with side length 3 units, volume 27 units ie 3 x 3 x 3 – we can also see there are 27 cubes)

5. ACTIVITY 4: Answer the following: 1. Order these from smallest to largest: 5 2 3 2 3 3 2 3 2 . Which of these numbers are also square numbers? 1 3 2 3 3 3 4 3 5 3 3 . Find two cube numbers that total 152 . 4. Explain why 125 is a cube number. 5. Write a number less than 100 in each space in this sorting diagram. Use short bond paper (handwritten or computerized) – utilize the folder of assignment 1 EVEN ODD A cube number Not a cube number

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