A hostel kitchen currently wastes 6% of the food it cooks. The warden wants the waste brought down to 4% of the same amount of food cooked. By what per cent must the wasted quantity fall?

Take 100 kg of food cooked: the waste must go from 6 kg to 4 kg. That is a fall of 2 kg measured against the present 6 kg: 2/6 = 1/3 = 33 1/3%. 2% is the drop in percentage points mistaken for a per cent fall - the two are different animals. 50% divides by the target 4 instead of the present 6. 66 2/3% is 4/6, the share of the waste that REMAINS rather than the share removed.