Euclidean Algorithm 
Greatest common divisor of \(a\) and \(b\) when \(a\) is a multiple of \(b\)
When \(a\) is a multiple of \(b\), the common divisors of \(a\) and \(b\) are the divisors of \(b\).
Hence, the greatest common divisor of \(a\) and \(b\) is the biggest divisor of \(b\), which is \(b\).
For example, the greatest common divisor of \(15\) and \(5\) is \(5\); the greatest common divisor of \(90\) and \(10\) is \(10\); the greatest common divisor of \(1000\) and \(25\) is \(25\).
