Question

The GCF of two numbers is 3.

Their LCM of the two numbers is less than 20.

Which could not be the two numbers?

Answer 1

Explanation:

Let say a and b the 2 natural integers with 0 < a< b.

Since a*b=GCF(a,b)*LCM(a,b)

a*b < 3*20=60

`\begin{array}ca&b&a*b&GCF&LCM&GCF*LCM\\---&---&---&---&---&---\\3&6&18&3&6&18\\3&9&27&3&9&27\\3&12&36&3&12&36\\3&15&45&3&15&45\\3&18&54&3&18&54\\6&9&54&3&18&54\\---&---&---&---&---&---\\\end {array}`