1. Finding HCF (3 numbers)
- Ladder Method

2. Recap-Highest Common Factor
Definition: The Highest Common Factor (HCF) of two or more given numbers is the highest (or greatest) of their common factors. It is also known as Greatest Common Divisor (GCD). Find the Highest Common Factor(HCF) of 12 and 16. Factors of 12 : 1, 2, 3, 4, 6, 12 Factors of 16: 1, 2, 4, 8, 16 The common factors of 12 and 16 are 1 , 2 and 4 Highest Common Factor(HCF) will be the highest of the given common factors – i.e. 4 Therefore HCF of 12 and 16 is 4.

3. Recap-Finding HCF by Ladder Method
Step 1: Divide the given numbers by their common factor other than 1 Step 2: Continue dividing till the only common factor left to divide is 1 Step 3: HCF is the product of all the common factors

4. Example 1: Find the HCF of 6, 12 and 24
Solution:
Step 1: Divide the given numbers by
their common factor other than 1
Step 2: Continue dividing till the only
common factor left to divide is 1
Step 3: HCF is product of all the common
factors
HCF (6 , 12 and 24) = 6
Ans: 6
Common
Factors 2 3
6 , , 24
3 , , 12
1 , , 4
There is no common
factor left other than 1 to divide so we stop here
HCF = 2 x 3 = 6

5. 13 13 , 26 , 39 1 , 2 , 3 Example 2: Find the HCF of 13, 26 and 39
Solution:
Step 1: Divide the given numbers by
their common factor other than 1
Step 2: Continue dividing till the only
common factor left to divide is 1
(in this case there is no need for this step
so we stop)
Step 3: HCF is product of all the common
factors
HCF (13, 26 and 39) = 13
Ans: 13
Common
Factor 13
, , 39
1 , , 3
There is no common
factor left other than 1 to divide so we stop here
HCF = 13

6. Example 3: Find the HCF of 84 , 70 and 28
Solution:
Step 1: Divide the given numbers by
their common factor other than 1
Step 2: Continue dividing till the only
common factor left to divide is 1
Step 3: HCF is product of all the common
factors
HCF (84 , 70 and 28) = 14
Ans: 14 7 2
, , 28
12 , , 4
6 , , 2
Common
Factors
There is no common
factor left other than 1 to divide so we stop here
HCF = 7 x 2 = 14

7. 14 , 27 , 32 Example 4: Find the HCF of 14 , 27 , 32 Solution:
Step 1: Divide the given numbers by
their common factor other than 1
HCF of two or more numbers that does not have a common factor is 1
HCF (14 , 27 and 32) = 1
Ans: 1
No Common Factors
, , 32

8. Try these
1. Find the highest common factor of 20, 28 and 36? 2. Find the highest common factor of 15, 30, 45? 3. Find highest common factor of 14, 56, 98?