Two 20-year-old members of the University of Sheffield Mathematical Society (UK), in partnership with the Debenhams store, devised a formula for decorating the perfect Christmas tree, ending bare branches or garish decorations and calculating the required amount of balls, ribbons, lights and the size of the star at the top.

To do this, you must first find the tree and, by its size, calculate the number of decorations. *“For example, a 180 cm (1.8 meter) Christmas tree would need 37 balls, about 919 centimeters of ribbon and 565 centimeters of lights, and it would take an 18 cm angel or star to finish”*, stress in a statement. The formula has been used in-store so consumers can choose their decorations at the right term.

And to calculate the number of balls is the square root of 17, dividing the result by 20 and multiplying by the height of the tree in centimeters; for the length of the tape, multiply 13 by Pi (3.1415), divide the result by 8 and then multiply by 3; for the length of the lights Pi must be multiplied by the height of the tree and for the size (in centimeters) of the star or angel to the top of the tree, the height of the tree should be divided by 10.

According to students Nicole Wrightham and Alex Craig, the formula allows customers to buy their Christmas decorations shrewdly, taking only what they need and leaving their tree well decorated. *“The formula took us about two hours to complete. We hope it makes preparing for Christmas a little easier. ”*Nicole Wrightham concluded.

The university also has an easy-to-use calculator, where you just put the tree size in centimeters and the rest is automatically calculated.

Source: *cienciahoje.pt*