# Blog

## Great to Meet You! brainteaser

By Ariel Marcy, 22 June 2023

Difficulty: Tricky You’ve just joined a new Scouts group! You meet 4 other new people, and everyone is going around giving handshakes. If everyone shakes hands with everyone else exactly once, how many handshakes will there be in total? (Remember you can’t shake hands with yourself.)

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## Regeneration brainteaser

By David Shaw, 8 June 2023

A sea sponge gets attacked by a shark and is ripped into 100 pieces. Luckily, sea sponges can join back together after they’ve been broken apart. Some pieces form into groups of 7, and the rest form into groups of 29. In the end, there are no pieces left. How many sponges do we end […]

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## Sequence This

By Ariel Marcy, 24 May 2023

Difficulty: Tricky Consider the following sequence of numbers. What number comes next? 1, 1, 2, 3, 5, 8, 13…

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## Sleepy time brainteaser

By Chenxin Tu, 10 May 2023

Lisa had a difficult time falling asleep on Wednesday night, so she began counting sheep. How many sheep did she count?

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## Circle gaps brainteaser

By Ariel Marcy, 26 April 2023

What is the area of the orange star in the centre? The blue circles each have an area of 3 square centimetres, and the big square has sides that are 4 centimetres long.

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## Trench diving brainteaser

By Ariel Marcy, 12 April 2023

Jing is taking her submarine to the bottom of an ocean trench. The first day she goes half the distance to the bottom of the trench.

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## Tricky triangle brainteaser

By Ariel Marcy, 29 March 2023

Time for a tricky triangle teaser! If the purple shaded triangle has an area of 2, what is the area of the largest triangle?

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## Prime number brainteaser

By David Shaw, 9 March 2023

Difficulty: Extreme 123,456,789 is not a prime number. Is it possible to reorder its digits to give a prime number?

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## George’s lollies brainteaser

By David Shaw, 23 February 2023

Difficulty: Extreme! George bought a bag of 70 lollies on Monday. He didn’t eat many on Monday, but he really liked the flavour. Every day after that he ate three more lollies than he had the previous day. The next Monday, George was about to eat his first lolly for the day and noticed the […]

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## Australian coins brainteaser

By David Shaw, 15 February 2023

Difficulty: Fun Jane has some Australian silver coins in her pocket. When buying an apple, she realises she has more than $1 in silver coins, but can’t make exactly $1 with her coins. How is this possible? (Silver Australian coins come in 5c, 10c, 20c, and 50c.)

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