An emty shipping box has a mass of 2.75 kilograms. An electronics store is packing 5 identical laptops in the shipping box. Each laptop has a mass of 1.65 kg.

The cost to ship the box was $40.00 for the first 5 kg and $3.15 for each kilogram over 5 kg. What was the cost to ship the packed box?

1. Add the total weight of the shipping box and it's inner items.

2.75 + (5*1.65) = 11 kilograms

2. Subtract the 5kg from 11kg to get the extra 6kg that was over 5kg.

3. Since it costs $3.15 for each kilogram and you have 6 kilograms, you just multiply the cost ($3.15) by 6 which is $18.9

4. Add together the costs of 5kg ($40) and 6kg ($18.9)

40+18.9=$58.9

The cost to ship the packed box was $58.9.