This activity encourages you to apply systematic strategies to ensure that you have found all of the ways of decorating the trees and have not missed any out. As an extension you could investigate the general rule for finding the number of different Christmas trees that could be decorated if there were n different colours to choose from and each tree had m lights.

Go to the Systematic Listing exercise for more practice.

There are solutions to each level of this puzzle showing the most efficient ways of lighting up the tree but they are only available to those who have a Transum Subscription.

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Friday, October 19, 2018

"I have seen many pupils doing this activity over the years. Some decide to concentrate on one tree at a time making sure all the tree’s lights are on before moving to the next tree. Other pupils will take a colour and go through the forest of trees turning on all the lights of that colour before moving onto the next colour. Other pupils (for the two colour levels) work from the outside trees in. They start with the outside trees each having lights of only one colour then as they work inwards they systematically reduce the number of lights of that colour after the relevant patterns have been exhausted. What is your preferred strategy?"