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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 […]

Difficulty: Extreme A teacher wrote a whole number on the whiteboard and asked her students to say what numbers it could divide by. The 1st student said, “the number is divisible by 1.” The 2nd student said, “the number is divisible by 2.” The 3rd student said, “the number is divisible by 3.” And this […]

Difficulty: Tricky Fernando has 3 water-tight containers that measure 3 cups, 9 cups, and 20 cups (for brevity, these are referred to as C3, C9, and C20, respectively). The containers have no markings to indicate other volumes, so there’s no way to know when a container is, say, half full. The containers have nice spouts, […]

Difficulty: Fun There are 50 total dogs signed up for a dog show. There are 30 more small dogs than large dogs. How many small dogs have signed up to compete in the show?

Difficulty: Fun Mariana the astronaut weighs 51 kilograms on Earth and 8.5 kilograms on the Moon. Mariana is training Javier to go to the Moon. If he weighs 78 kilograms on Earth, how much will he weigh on the Moon?

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.)

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 […]