LCM( 1240, 645 ) = 159960
The formula for finding LCM is
$$ \text{LCM} (a, b) = \frac{ a \cdot b }{ \text{GCD}(a,b)} $$In this example we have: a = 1240, b = 645 and GCD(1240, 645) = 5.
$$ \text{LCM} (1240, 645) = \frac{ 1240 \cdot 645 }{ \text{GCD}(1240,645)} = \frac{ 799800 }{ 5 } = 159960 $$