Find the HCF and LCM of 40 and 60, we write them as prime factors
$40=2^3\times 5$ and
$60=2^2\times 3 \times 5$
LCM(40 and 60)$=2^3\times 3\times5=120$
HCF(40 and 60)$=4\times5=20$
How do I find the HCF and LCM of 40 and 60 using a Venn diagram method?
You already know that $40=2\times2\times2\times5$ and $60=2\times2\times3\times5$ so every time there is a prime factor in common, it is put into the middle the the two circles as shown below. What is left of each number is put to the left/right of the middle respectively. $\require{HTML}\newcommand{\mypic}[4][]{\style{display:inline-block;background:url(https://i.stack.imgur.com/#4)no-repeat center;#1}{\phantom{\Rule{#2}{#3}{0px}}}}$ \begin{array}{cc}\mypic{350px}{250px}{5am8u.png}\end{array} The HCF is found by multiplying everything in the middle of the two circles to give $2\times2\times5=20$ and the LCM is found by multiplying every number in the Venn diagram to give $2\times(2\times2\times5)\times3=120$.