Question

The HCF of 144 and 198 is ______.

Options

• 9

• 12

• 6

• 18

Answer 1

The HCF of 144 and 198 is 18.

Explanation:

2 × 3² = 18

We first factorise the two numbers:

2	144
2	72
2	36
2	18
3	9
3	3
	1

 

2	198
3	99
3	33
11	11
	1

144 = 2 × 2 × 2 × 2 × 3 × 3 

= 2⁴ × 3²

198 = 2 × 3 × 3 × 11

= 2 × 3² × 11

Here, 18 (2 × 3² = 18) is the highest common factor of the two numbers.