Today Puzzle #639
Puzzle No. 639 鈥� Tuesday 24 December
This year we're buying a smaller Christmas tree. It's half the weight of last year's tree. Last year we needed 12 metres of tinsel and 24 baubles to decorate the tree tastefully. Using the same decorations as last year how much tinsel and how many baubles will we need this year?
Today’s #PuzzleForToday has been set by Hugh Hunt, Reader in Engineering Dynamics and Vibration at Trinity College, Cambridge
Click here for the answer
9.5 metres of tinsel and 15 baubles
The height and width of the tree goes as the cubed root of its weight. So the height and width are 0.79 times those of last year's tree. The tinsel needs to cover the distance so 0.79 * 12 is 9.5m
The surface area goes as height squared, so the area to decorate is 0.63 times that of last year
Assume that the bauble decoration density (tastefulness?) is the same as last year then the number of baubles goes down by the area, 0.63*24 = 15
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