Today's real life maths story is about difficulties with oranges.

Almost everyone in their life needed to find the best value of some goods. Shall you get a bigger package or the package at a sale? For some people, it's everyday question. It helps us budgeting, so I recommend to master it.

Anyway, the other day we find out at home nowadays all usual orange supplies from markets are waxed. The problem for us vegans is the wax is from an animal source.
And I'm fairly orange addicted, so we had to have a look at organic, unwaxed oranges.
Our brief look at the internet gave us these few options to compare:
Sainsbury's organic oranges - 4x per £1.75
organic oranges from an online delivery company - 8 kg per £14.20
Tesco organic oranges - 5x per £1.75
One more information from the Tesco site was that typical orange is 155 g.

The trouble here is, someone gives the price per orange, someone per kilogram. How to work this out? We need to work out different units and convert them. At the end, we can either compare price per orange or price per 1 kg. (Another usual way is to work out how much of the goods can we get for £1 or any reasonable amount of money.)

Here we had two sources in terms of oranges and money per pack, so the easiest way was to work out the bulk 8 kg into a number of oranges.

First to get the easy bits: we know already the price is same and we'll get more oranges in Tesco, so obviously the price per orange is better there than in sainsbury's. But out of curiosity, we can work out the figures to see the difference:
Sainsbury's £1.75 / 4 = £0.44
Tesco £1.75 / 5 = £0.35But how about now the online delivery?
If one orange is typically 155 g according to information we gathered before, we'll use it as a guide to work out how many oranges are in 1 kg and later in 8 kg.

1 kg = 1000 g
1000 / 155 = 6.45 (reasonably rounded)
8 kg -> 8 x 6.45 oranges = 51.6 oranges (of roughly 155 g mass each).
Hooray! Almost there =)

Price per our 51.6 oranges in 8 kg is £14.20, therefore £14.20 / 51.6 = £0.28 per one orange from the online delivery company.

The last bit is to find out the price of delivery and find out whether it's still better than go to the nearest Tesco (or what's the price for delivery from this place).
Another thing to consider may be the actual mass of those oranges if any of them would significantly differ from the mass (155 g) we work with above.
All of there are just small things to consider, but the main maths is done the way I showed here.

I should mention my partner did this whole maths on his own =) So even if you finished with your maths at GCSE level decade ago, you will still use this level of maths knowledge in your life.