4.2 A better solution
Here is an improved solution which shows working.
Suppose you plan to redecorate your bathroom. The end wall has the following shape, with dimensions as shown on the diagram. The quality of the plasterwork is not good and you are considering tiling the wall.
Write down the area of this wall. 
Solution B to Example 13
Here the area is broken down into manageable parts and each area is found before the total area is stated. Had one of the areas been wrongly calculated, only one mark would have been deducted and the remainder would have been marked on a ‘follow through’ basis, giving almost full marks when a small error has been made. ‘Follow through’ means that credit is given for the method, even though the wrong value has been used.
When asked to ‘write down’ a solution, try to judge how much working to give by looking at the number of marks available for a correct solution.