Today Puzzle #712
Puzzle No. 711 鈥� Tuesdday 7 April
Tonight is a "Super Pink Moon". It won't look pink though - it'll be more of a dusty orange. It's called a "Super" moon because it will be about 15% bigger than an ordinary full moon. If you hold up a coin at arms length you can cover the whole of the disc of the moon. What is the smallest coin, held at arm's length, sufficient to cover the entire moon?
Today’s #PuzzleForToday has been set by Dr Hugh Hunt, Reader in Engineering Dynamics and Vibration at Trinity College, Cambridge
Click here for the answer
One-third the diameter of a 5-pence coin. You can look at the full moon through one of the holes in a piece of hole-punched paper held at arms length. The moon fills the 6mm-diameter hole perfectly. The moon is 3500km and about 350,000km away (the actual distance depends on time of year because the moon moves on an elliptical orbit) Taking "arms length" as about 600mm then by similar triangles the size of the "coin" is about 6mm. A British 5-p coin is 18mm in diameter.
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