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