Euclidean Algorithm 
How can we find the g.c.d. of two numbers without listing all their divisors?
Before answering this question, we start by looking at some particular cases and an important property.
What are the common divisors
of \(a\)
and \(b\)
when \(a\)
is a multiple of \(b\)?
What is the
greatest common divisor of \(a\)
and \(b\)
when \(a\)
is a multiple of \(b\)?
If \(a=b+c\),
what is the a relation
between the common divisors of \(a\)
and \(b\)
and the common divisors of \(b\)
and \(c\)?
With the answers to these questions we can eventually see the Euclidean algorithm to find the greatest common divisor of two numbers.
