Word problems in context
Turn the words into one calculation at a time, then ask what kind of answer the situation actually needs.
A worked example
A jar of paint covers 11 m² and the wall is 26 m². Since 26 / 11 = 2.4, buy 3 jars, because part of a jar cannot be bought.
The mistake people actually make
A discount and then a tax are two separate steps, applied in that order. A 'how many whole items' answer rounds down, even when the decimal part is large.