Question

If the LCM of two numbers $21$ and $30$ is $210$, what is their HCF?

Answer 1

Let Suppose we have two numbers $a$ and $b$, then we have a rule i.e $a\times b=HCF(a,b)\times LCM(a,b)$, which means that product of those two numbers is equal to the product of their LCM and HCF

Given : $a=21,b=30andLCM=210$

so using the property, we have $21\times 30=HCF(a,b)\times 210$

$\frac{21\times 30}{210}=HCF(a,b)$

$3=HCF(a,b)$