LCM( 10, 15 ) = 30
The formula for finding LCM is
$$ \text{LCM} (a, b) = \frac{ a \cdot b }{ \text{GCD}(a,b)} $$In this example we have: a = 10, b = 15 and GCD(10, 15) = 5.
$$ \text{LCM} (10, 15) = \frac{ 10 \cdot 15 }{ \text{GCD}(10,15)} = \frac{ 150 }{ 5 } = 30 $$