Math Ch-3 Cube and Cube roots

 14/08/20

Topic Taught: 1. Cube of a number

2. Properties of cube numbers

3. Perfect cube

Reference Video Links:

1. Watch Video given in Link 1 based on Cube of a numbers.

2. Watch Video given in Link 2 based on Perfect Cube numbers.

4. Watch Video given in Link 3 based on properties of a cube numbers. (watch till 2:59 duration only)

5. Watch Video given in Link 4 based on properties of a cube numbers.

Cube of a number: The cube of a number is the product obtained when a number is multiplied by itself three times. That is, if x is a number then its cube is x^3.


Properties of cube number:

1. There are only ten perfect cubes from 1 to 1000.

2. The cube of an even number is even and an odd number is odd.

3. The cubes of the numbers with last digits 1, 4, 5, 6, 9 and 0 have the same last digit.

4. If the last digit of a number is 2, then the last digit of its cube is 8.

5. If the last digit of a number is 3, then the last digit of its cube is 7.

6. If the last digit of a number is 7, then the last digit of its cube is 3.

7. If the last digit of a number is 8, then the last digit of its cube is 2.

8. The cube of a positive number is positive. The cube of a negative number is negative.

For example, the cube of 2 is = 2 × 2 × 2 = 8 and the cube of –2 is  = (–2) × (–2) × (–2) = –8.

9. The product of two perfect cubes is also a perfect cube.

For example, 8 and 27 are perfect cubes.  and 8 x 27 =216 , 216 is also a perfect cube.

Prime Factorisation to Check if a given Number is a Perfect Cube: 

To check if a given number is a perfect cube by prime factorisation method.

i. First write the number as the product of its prime factors.

ii. Then group the triplets of equal factors.

If all the factors can be grouped in triplets of equal factors then the given number is a perfect cube.

Format -Q3 of Exercise 3.1


Homework: Complete Exercise 3.1 Q 1,3 in notebook and Q2 in textbook.


17/08/20

Topic Taught: 

Application of cube number

Finding cube root by prime factorization method


1. Watch the Video given in Link 5 based on application of cube number.

2.Watch Video given in Link 6 based on to find cube root of a number using the Prime Factorization Method.


Classwork: Ex 3.1 Q4- a,e Q5 - b,d Ex 3.2 Q1- a Q3- c

Exercise 3.1






Exercise 3.2


Homework: Please complete remaining sums of Exercise 3.1 Q4 and Q5 ,Exercise 3.2 Q1 and Q3.



18/08/20

Topic Taught: 

1. Application of cuberoots.

2. Cube Root of a Cube Number through Estimation.


Watch the Video given in Link 7 based on cube Root of a cube number through estimation.


Classwork :



Estimation of cube root: Exercise 3.2 Q2



Homework: Complete Exercise 3.2 Q 4 - b,c,d . Revise all the topics taught.

19/08/20

Topic Taught: Revision and Discussion of Workbook Exercise.

Homework: Complete Workbook and Worksheet Exercise. Submission of Workbook and worksheet for Ch-3 will be on 25/08/20.



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