Step-by-step explanation:
£480 = 120% (after adding the 20% VAT).
we want to know how much 100% is.
he do we get from 120% to 100% ?
first the formal long way
£480 = 120%
1% = 120%/120 = 480/120 = £4
100% = 1% × 100 = 4×100 = £400
once you understand this mechanism, you can apply the direct shortcut :
£480 / 1.2 = £400
as a multiplication with 100/120 is the same as a division by 120/100, which is 1.2.
and what we did at the beginning in long form was nothing else than
£480 × 100/120 = 480 × 10/12 = 480 × 5/6 = £400
