CLASS: VIII SUBJECT:- MATHS CUBES AND CUBE ROOTS PERIODS COUNT __1
LEARNING OBJECTIVES
To make students understand:
Definition of cube
Perfect cubes
Properties of cubes
Concept
Cube roots
Methods of finding Cube Root of a number
Estimating Cube Roots
Students will be able to
Define cube number/ perfect cube
Classify the given numbers as cube numbers or non-cube numbers.
Find cube of a number using various methods
Skills
Identify cube root
Find cube root using prime factorization
Find cube root of a rational number
Estimate cube roots
Facts:
A number which when multiplied by itself thrice is a perfect cube of that number.
The cube/cube root of any positive number is always positive.
The cube/cube root of any negative number is always negative.
The sum of cubes of the first n natural numbers equals to the square of the sum of
those numbers.
( )
2
n ( n+1 )
13 +23 +33 +4 3 +53 … n3=(1+2+3+4 +5 …+n)2=
2
()
3 3
a a
Cube of a rational number = 3.
b b
Facts &
Misconceptions Cube root is the opposite of Cube.
Amazing fact:
Numbers like 1729, 4104, 13832, are known as Hardy – Ramanujan number.
Misconceptions:
Incorrect Correct
3 3
5 = 5 x 3 = 15 5 = 5 x 5 x 5 = 125
Cube root of x = 3 √ x Cube root of x =√3
x
Cooperation
Value
Helps in developing self confidence
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, Vocabulary/ Cube/perfect cube, cube root, prime factorization, estimation
Keywords
TEACHING AIDS/ RESOURCES
Concept map, book
CLASS: VIII SUBJECT:- MATHS CUBES PERIODS COUNT __2
ACTION PLAN
Teacher will activate the prior knowledge by asking questions:
Prior Knowledge 1. What is the cube of 4?
2. What is a perfect cube?
Teacher will introduce the concept of cubes through concept map and explanation.
cubes
properties of
cube roots
cubes
by prime
estimation of
factorisation
cube roots
method
Plan execution Definition of cube: A number which when multiplied by itself thrice is a perfect cube of
that number. The cube of a number is that number raised to power 3. Thus, if x is a number,
then the cube of x is x3.
For example:
1x1x1 =1 = 13 , 2x2x2 =8=23 , 3x3x3 = 27=33 , …
The number 1, 8, 27 are obtained on multiplying each of 1, 2, 3 respectively by itself 3
times. The numbers 1, 8, 27 … are called Perfect cubes.
Numbers Cubes
1 1
2 8
3 27
4 64
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