by David, 7 December 2020 | 0 comments

Difficulty: Extreme I’m thinking of a number. When you add one and a half to it, you get the same result as if you multiplied it by one and a half. What’s the number I’m thinking of?

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by David, 25 November 2020 | 0 comments

By Rok Willesee Difficulty: Fun An engineer has asked you to help him count the number of triangles in this roof truss. He thinks there are five, but his boss thinks there are more. How many triangles can you see?

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by Fiona, 11 November 2020 | 0 comments

Abelina and Ben bought a bag of jelly beans, and decided to split it. When they shared the jelly beans out, they split evenly and there wasn’t any remainder.

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by David, 28 October 2020 | 0 comments

By Rok Willesee Difficulty: Tricky A scientist was looking back at notes they made about their experiments. Unfortunately, in one experiment the scales didn’t work. Can you help them work out what the weight should be in the final experiment?

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by David, 14 October 2020 | 3 comments

Difficulty: Taxing Jenny found a strange sum written on a piece of paper: EGG + EGG = PAGE Each letter represents a different digit, so P might be 1, for example. Can you work out what the sum really is?

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by David, 30 September 2020 | 0 comments

Difficulty: Taxing Grab a calculator (or a pen and paper) Choose a three-digit number (e.g. 123) Multiply it by 7 Multiply the answer by 11 Multiply that answer by 13 You will get your starting number written out twice! (e.g. 123 123) The question is, can you work out why?

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by David, 16 September 2020 | 1 comments

Difficulty: Tricky We’re going to make a magic triangle! Take the numbers 1–6 and arrange them in a triangle with three numbers on each side. Swap them around until the sides all add up to the same number.

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by David, 26 August 2020 | 1 comments

Difficulty: Taxing Here’s a beautiful artwork from 1895, titled Mental calculation. In public school of S. A. Rachinsky, painted by Nikolay Bogdanov-Belsky. Can you solve the puzzle the kids are pondering? If you can’t quite see the equation, here it is:

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by David, 19 August 2020 | 0 comments

Difficulty: Tricky Gertrude has a collection of shapes that she likes to arrange in patterns. She starts with a regular hexagon with 10 cm sides, and three regular triangles that also have 10 cm sides. She arranges the triangles around the hexagon, and then lines them up. In the end, one side of each triangle…

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by David, 3 August 2020 | 4 comments

Difficulty: Fun I’m thinking of three numbers. They are consecutive counting numbers. When you add the first two numbers together, you get the third number. What numbers am I thinking of?

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