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Calculator Keys at the Corners of a Rectangle

Thursday 1st November 2018

Type a four digit number on to your calculator. The keys used to type in this number must form a rectangle. Each digit should be one of the corners of this rectangle and you can work your way around this rectangle either clockwise or anticlockwise starting at any corner of the rectangle.

Calculator Keys

After you have created many four-digit numbers using this method you should see that all of the numbers have something in common. They are all divisible by the same prime number. What is that number?

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