Question

500ml bottle unit cost is $2.10

Answer 1

If you would like to know what is the unit price for the hair shampoo, you can calculate this using the following steps:

500 ml ... $2.10
100 ml ...$x = ?

500 * x = 2.10 * 100    /500
x = 2.10 * 100 / 500
x = $0.42

The unit price for the hair shampoo is $0.42.