Unit pricing
The unit price of something is the price for a fixed amount (usually the price per 100g, price per ml or price for one bar etc.) It is used in supermarkets to help customers compare the price of different sized items. When comparing, it is very important to use the same units when calculating the unit price.
Unit price is calculated by dividing the price by the mass (or volume or number of bars etc).
Eg Unit price = \(\frac{\text{price}}{\text{mass}}\)
Example
Which packet of biscuits is better value for money?
- 拢1 for 400 g
- 拢1.90 for 1 kg
It is hard to decide which item is better value if they are different sizes.
400 g packet
Unit price = \(\frac{\text{price}}{\text{mass}}\)
Unit price = \(\frac{100}{400}\)
The small packet cost 0.25 pence per gram.
1 kg packet
Unit price = \(\frac{\text{price}}{\text{mass}}\)
The units must be the same for the prices to be compared, so first convert kilograms to grams. 1 kg = 1,000 g.
Unit price = \(\frac{190}{1,000}\)
The large packet costs 0.19 pence per gram.
So the large packet is better value as the unit cost is lower.