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Holly loves drawing and her favourite colours have been sharpened a lot. Her most favourite colour, rose, is exactly 3cm long. She discovers that the teal pencil is exactly 4cm, and the almond pencil is exactly 6cm. What lengths from 1-10 cm can Holly make with her pencils?

In 2023, Double Helix readers busted a bunch of brainteasers! Here are the tippy-top, most popular puzzles of the year.

Can you find a different set of 5 positive whole numbers with the same stats?

Difficulty: Fun Ellen has a set of 6 weights that come in pairs. One pair is a magical set of negative weights (think helium balloons that take weight away). 2 of the weights are 1 kilogram each, 2 of the weights are 5 kilograms each, and the 2 magical weights are -3 kilograms each. Ellen […]

Difficulty: Fun Triangular numbers are numbers that can be formed into a triangle. For example, 3 is a triangular number with 2 dots on the bottom row and 1 dot on top row forming an equilateral triangle of 3 dots. 6 is the next triangular number with 3 dots on the bottom, 2 dots in […]

Difficulty: Tricky Anas is making a map of his friend group. In his map, each circle is a person. A line joins 2 circles if and only if those 2 people are friends. Using the clues below, can you figure out who goes where on the map? 1. Anas has 3 friends: Ruth, Mitra, and […]

Difficulty: Tricky Ahmad’s computer scientist mother gives him a binary stopwatch that counts minutes using only 1’s and 0’s – just like a computer! The binary stopwatch has 6 placeholders where the 1’s and 0’s appear. When the binary stopwatch is reset, all the placeholders are zeros. Ahmad finds a regular stopwatch, resets both stopwatches, […]

Difficulty: Tricky You have 2 glasses, each filled with 100 millilitres (ml) of soda. One contains cola and one contains orange soda. First, you take a spoonful of cola and mix it into the orange soda. Next, you take an equal spoonful of the orange-cola mixture and put it into the glass of cola. Which […]

Difficulty: Fun The big rectangle below is made from 4 small rectangles. All the small rectangles are equal, meaning that they have the same size and shape. If the small rectangle’s short side is 8 centimetres, what is the length (long side) of the bigger rectangle?

Difficulty: Tricky Alex is playing a dice game with 2 standard 6-sided dice, one red and one blue. Each die has faces numbered from 1 to 6. Alex rolls both dice and adds up the numbers on the top faces. After a while, Alex notices that the sums are always between 2 and 12 and […]