Suppose that you are asked to calculate the amount of aluminium, required to get 1120 kg of iron by the above equation.

Aluminium —» Iron

54g-------------->112g

x ? --------------->(1120 x 1000)g

xg = (1120 x 1000) g x 54 / 112 g

= 10000 x 54 = 5, 40,000 or 540 kg

1120 kg of iron we have to use 540 kg of aluminium.