Final answer:
The cost of 400g at 25p per kg is 10p, calculated by converting grams to kilograms and then multiplying by the price per kilogram.
Step-by-step explanation:
To calculate the cost of 400g of an item at 25p per kg, we first need to convert the weight from grams to kilograms, since the price is given per kilogram. There are 1,000 grams in a kilogram, so 400 grams is equivalent to 0.4 kilograms. The next step is to find the cost by multiplying the weight in kilograms by the price per kilogram.
Therefore, the calculation is as follows:
This means the cost for 400 grams at 25p per kg is 10p.