Cube of Numbers
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Cube of Numbers : The number with exponent 3 is called cube.
The word ‘cube’ is used in geometry. A cube is a solid figure which has all its sides equal.
There are only ten perfect cubes from 1 to 1000.
If a number is a number, then the cube of a is a 3 ,
a x a x a = a 3
Examples
1. 2 3 = 2 x 2 x 2 = 8, that is the cube of 2 is 8.
2. 3 3 = 3 x 3 x 3 = 27, that is the cube of 3 is 27.
3. 4 3 = 4 x 4 x 4 = 64, that is the cube of 4 is 64.
4. (1.2) 3 = 1.2 x 1.2 x 1.2 = 1.728
5. (2/3) 3 = 2/3 x 2/3 x 2/3 = 8/27
A natural number is said to be a perfect cube if it is the cube of some natural number.
Example
8 = 2 x 2 x 2
8 = 2 3
8 is the perfect cube because it is a cube of 2 which is a natural number.
But 12 is not a perfect cube because it is not a cube of any natural numbers.
Practice
Q.1 Find the cube of :
1) 6 3
2) (-7) 3
3) b 3
4) (1/8) 3
5) (0.5) 3
Q.2 Which of the following numbers are perfect cube.
1) 125
2) 15
3) 27
4) 36
5) 343
6) m 3
7) 1/8
8) 27/216
9) -1/64
10) 49/729
Cube and Cube Roots
• Cube of Numbers
• Perfect-Cube
• Properties - Cube
• Cube by Column method
• Negative numbers-cube
• Cube - Rational numbers
• Cube-Root
• Finding cube root by Prime Factorization
• Cube root of Rational numbers
• Estimating cube-root
Number Sense
8th grade math
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