LCM( 5, 3 ) = 15
The formula for finding LCM is
$$ \text{LCM} (a, b) = \frac{ a \cdot b }{ \text{GCD}(a,b)} $$In this example we have: a = 5, b = 3 and GCD(5, 3) = 1.
$$ \text{LCM} (5, 3) = \frac{ 5 \cdot 3 }{ \text{GCD}(5,3)} = \frac{ 15 }{ 1 } = 15 $$