I recently received a publications list and order form. I want to order seven items from the list. However, I noticed that the structure of the postage and packaging charges was very strange, as shown in the table below:

I have decided that I will ask them to pack my order in the number of parcels that will have the lowest postal charge.

What is the lowest postal charge for my seven items?

Determine what they are trying to ask, and what you will need to solve it

Eliminate any non-essential information

Draw a picture, graph, or equation

In moments of high stress like exam taking, always work with the paper they give you to avoid careless mistakes.

Solve.

This is a question that does not really have the best approach, but rather is more of a ‘guess and check’ on how to find the cheapest combination. First, let’s understand the question, you have 7 items that need postal, but you need to find the best price because they are not straightforward.

We can instantly eliminate C, because it is more than double the price of shipping 5 items at once.

Now we can start to combine:

5 items + 2 items £1.60 + £0.70 = £2.30
(not even an option)

4 items and 3 items £1.30 + £0.95 = £2.25
This is the second lowest price out of our available options! Now we know it is either A or B.

Just looking at the table and running various other combinations in our head, doing extremely loose calculations, it is impossible to make 7 items less than even £2.00. So we can conclude that A is incorrect as well.

\fcolorbox{red}{grey!30}{Therefore E, $£2.25$ is the correct answer.}