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
![\left[\begin{array}{ccc}1&2&3\\4&5&6\\7&8&9\end{array}\right]](https://tex.z-dn.net/?f=%20%20%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D1%262%263%5C%5C4%265%266%5C%5C7%268%269%5Cend%7Barray%7D%5Cright%5D%20)