Twelve gift boxes require 46 metres of ribbon when each box is decorated identically. How many metres of ribbon do 18 boxes require? Enter the number of metres.

Explication

The box count changes by a factor of 18 divided by 12, which is 1.5, so the ribbon becomes 46 times 1.5, or 69 metres. Adding the increase of six boxes to 46 would give 52 metres, but direct proportion matches scale factors rather than equal additions.