Question

Find the H.C.F of 90 and 162.

• A. 9
• B. 18
• C. 27
• D. 3

Answer 1

The correct option is B 18

Using prime factorisation method:

$\begin{array}{cc}2& 90\\ 3& 45\\ 3& 15\\ 5& 5\\ & 1\end{array}$

$\therefore 90=2\times 3\times 3\times 5$

$\begin{array}{cc}2& 162\\ 3& 81\\ 3& 27\\ 3& 9\\ 3& 3\\ & 1\end{array}$

$\therefore 162=2\times 3\times 3\times 3\times 3$

$90=2\times 5\times 3\times 3$
$162=2\times 3\times 3\times 3\times 3$

$\therefore$ The HCF is $2\times 3\times 3=18$