We know the following relation between pounds (lbs) and kilograms (kg):
[tex]1\text{ }lb=0.4536\text{ }kg\Rightarrow1=\frac{0.4536\text{ }kg}{1\text{ }lb}.[/tex]The unit-factor method consists in multiplying the quantity expressed in pounds by the expression above and then cancelling the lb to obtain the result in kg:
[tex]120\text{ }lb\times\frac{0.4536\text{ }kg}{1\text{ }lb}=(120\times0.4536)\times kg=54.432\text{ }kg.[/tex]Answer120 lb = 54.432 kg
