Question

Find the HCF and LCM of 90 and 144 by prime factorisation method.

• A. 18 and 720
• B. 720 and 18
• C. 360 and 180
• D. 180 and 720

Answer 1

The correct option is A 18 and 720

Prime factorisation of 90 and 144:
$90=2\times 3\times 3\times 5$
$144=2\times 2\times 2\times 2\times 3\times 3$
$\Rightarrow \text{HCF}=2\times 3^2=18$
$\text{LCM}=2^4\times 3^2\times 5=720$
$\therefore$ HCF and LCM of 90 and 144 are 18 and 720 respectively.