# Blog

## Massive multiplication

By David Shaw, 10 April 2024

Sienna’s teacher is writing up a wicked problem. First, the teacher writes all the numbers from 1 to 99 and then erases 10, 20, and all the other numbers that end in 0. “Listen up! Multiply all these numbers. Tell me the last digit and I’ll give you full marks on your next assignment.”

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## Secret pairs

By Ariel Marcy, 12 March 2024

Lavonne is testing a secret code with her friend Jack. First, she picks 3 different secret numbers between 1 and 9. Then she finds the sum of each pair of numbers. Lavonne wants to know if Jack can figure out the original secret numbers just from the sums?

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## Brainteaser: Egg-cellent farming

By Ariel Marcy, 26 February 2024

Farmer Wallace packages his eggs in cartons that hold a dozen eggs. In March, he sells 5 standard orders of eggs to the local grocery store. Each standard order consists of 4 grosses of eggs. A gross is 144 eggs. How many cartons of eggs did Farmer Wallace sell?

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## Brainteaser: Space climb

By Ariel Marcy, 13 February 2024

Catalina won a game show prize! She spent 3/4 of it on a trip into space. She spent 2/3 of her remaining money climbing Mount Everest. Finally, she donated the last $100,000 to wildlife. How much did she win?

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## Same, same, same but different

By Ariel Marcy, 6 December 2023

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

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## Magical weights

By Ariel Marcy, 14 November 2023

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 […]

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## Nifty triangle numbers

By Ariel Marcy, 6 November 2023

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 […]

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## Friendship circles

By Ariel Marcy, 23 October 2023

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 […]

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## Crack the computer clock

By Ariel Marcy, 4 October 2023

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, […]

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## Soda Smash-up

By Ariel Marcy, 27 September 2023

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 […]

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