How many cubic centimetres make a litre?

If the tin (cylinder) had a diameter of $10 \; \text{cm}$ what would the height be?

What surface area would this tin have? Don't forget the top and the bottom.

Would a diameter of $20 \; \text{cm}$ have a greater or lesser surface area?

Can you write out a procedure to follow for any diameter you have to try?

Try to follow your procedure and use trial and improvement to get increasingly close to the diameter which gives the lowest value for the complete surface area.

What was the height for that radius value?

What was the proportion between the height and the diameter?

A spreadsheet might be useful once you are sure of your method.