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BrainTwister #9: Rectangulator

Can you solve this week’s logic puzzle? Plus our quick quiz and the answer to last week’s problem

By New Scientist

28 February 2024

New Scientist. Science news and long reads from expert journalists, covering developments in science, technology, health and the environment on the website and the magazine.

#9 Rectangulator

Set by Katie Steckles

Given a standard calculator keyboard, press – in order, going either clockwise or anticlockwise – four digit keys that form the corners of a square or rectangle on the keypad. This will create a four-digit number, e.g. 7469.

If the first button you press is the 7 key, how many possible four-digit numbers can you create?

What about if your square or rectangle is allowed to have a height or width of zero?

Can you show that for any square or rectangle you choose, the resulting four-digit number will always be divisible by 11?

Solution next…

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