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Alice forgot the code to get into her computer. She knows it was a number with three digits, like 286 or 935. All she can remember is that the first digit is the second digit minus 3. The second digit is 4 times the third digit. And two of the digits are the same. Can you help Alice get into her computer?

Kim has a big round cheese, and an even bigger knife. With three straight cuts, what’s the largest number of pieces she can cut?

An adventurous snail decides to climb up a wall to the roof of a school. The snail can climb up 3 metres in a day but slides back down 2 metres at night! If the school is 12 metres tall, how many days will it take the snail to reach the roof?

Sam arrives first to her after school Maths Club meeting. She discovers that her teacher has left a basket of Valentine’s Day chocolates. It comes with the instructions to share the chocolate evenly among the six students in the club… but Sam eats a few chocolates before anyone notices!

Rita is making lamingtons for her birthday party and cuts them precisely into 5-centimetre cubes. While playing around with an antique balance scale, she discovers that one lamington is equal to 50 grams plus half a lamington. At her party, she eats one and a half lamingtons. How much did Rita’s dessert weigh?

Double Helix Extra readers really got busy with brainteasers in 2024! Let’s do a count down of your top 5…

Here are eight 8s, 8 8 8 8 8 8 8 8. Put some plus signs in there to make 1000.

A famous person built a square house so that the windows on all four sides look south. Where is this house? (And can you name the famous person?)

Farmer Doolittle has a farm with just cows and chickens. The farmer counts up all the animals and discovers that there are 43 heads and 120 legs on the farm (not counting the farmers). How many cows live on farmer Doolittle’s farm?

We’ve written a code using two different prime numbers less than 10. We then multiplied these two primes and used the resulting “code number” to shift the alphabet forward to new letters. Can you use the clues above to decode this message: DRO QYVN SC LEBSON SX DRO QKBNOX.