A garment unit's monthly wage bill is the number of workers × the days worked in the month × the daily wage. Next month it will take on 20% fewer workers, work 25% more days and pay each worker 20% more per day. Its wage bill will show:

The three changes multiply: $0.80\times 1.25\times 1.20=1.20$, a rise of 20%. Notice that the 20% cut in workers and the 25% rise in days cancel exactly $(0.80\times 1.25=1)$, so the whole rise is the wage rise. (Adding the three figures as −20 + 25 + 20 gives 25%. Applying only the two rises, $1.25\times 1.20=1.50$, gives 50% and forgets the smaller workforce; taking 20% off THAT, as 1.50 − 0.20 = 1.30, gives 30% by subtracting a percentage of the wrong figure.)