The answer is $1.8 This is because if 5kg equals $9. So we have to find out what 1kg is equaled to and to get from 5kg to 1kg, we have to divide by 5. We have to divide $9 by 5 as well to get the price. And 9 divided by 5 is $1.8. This is just how ratio works. You can also lay it out like this: 5kg : $9 ⬇️(➗by 5) 1kg : $1.8