# Blog

## Guarding the castle brainteaser

By David Shaw, 3 December 2021

Difficulty: Tricky There are 32 soldiers guarding a square castle. The castle has 8 towers – one in each corner of the square, and one in the middle of each side. The soldiers want to make sure all the walls are guarded.

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## A crowded bus brainteaser

By David Shaw, 24 November 2021

Difficulty: Fun The number 39 bus was packed as it pulled into the interchange. Then 37 people got off, and another 14 got on. As the bus left the interchange, there were 37 people on board. How many people were on the bus as it pulled into the interchange?

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## Joining five dots brainteaser

By David Shaw, 10 November 2021

Difficulty: Extreme! Ziqi’s teacher loved puzzles, and posed a difficult challenge: “Draw five dots on a piece of paper. Now, connect each dot to every other dot. Each pair of dots needs to be connected by a line, which doesn’t need to be straight.”

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## Coloured cups brainteaser

By David Shaw, 20 October 2021

Difficulty: Tricky Scarlett, Azure and Jett were drinking tea together. There was one scarlet red teacup, one azure blue mug and a jet-black tea glass. None of them had a cup that was the same colour as their own name. After a while, Scarlett offered to get the person with the black glass another drink. […]

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## Reshuffling cars brainteaser

By David Shaw, 13 October 2021

Difficulty: Extreme! Terri runs a car showroom. It has 3 roads to park cars on, which all meet in the middle of the showroom. Terri can fit 3 cars on each road. If she tries to park a fourth, it blocks the intersection in the middle. At the moment, there are 2 Audis on one […]

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## Time to shake brainteaser

By David Shaw, 30 September 2021

Difficulty: Tricky Last week, there was an earthquake near Mount Buller in Victoria. The shaking reached central Melbourne around 9:16:30, and Canberra at 9:17:30. It’s 120 kilometres from the earthquake epicentre to central Melbourne, and 360 kilometres from the epicentre to Canberra. From the epicentre to Sydney, it’s 600 kilometres. What time did the shaking […]

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## How many hats? Brainteaser

By David Shaw, 13 September 2021

Difficulty: Extreme! The geology club was on its way to check out a fault line. As the minibus cruised down the highway, several club members realised they had forgotten their hats.

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## Hungry giraffes brainteaser

By David Shaw, 26 August 2021

Difficulty: Tricky Kimya the giraffe can eat a bale of hay in 3 days. Little Azizi can eat a bale of hay in 6 days. If they both share a bale of hay, how long would it last?

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## Starry banner brainteaser

By David Shaw, 18 August 2021

Difficulty: Tricky Kirk is designing a banner for an astronomy club. They want to put some stars on the banner, in straight lines.

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## Shrinking square

By David Shaw, 5 August 2021

Difficulty: Fun Alex has a square of paper, but it’s a bit too big. To make it smaller, they found the middle of each side, and then ruled lines between them. Then they cut off the four corners along the lines, leaving a square in the middle.

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