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Difficulty: Tricky Ben is driving his train slowly. He realises he’s left an important package in the last car of the train. He needs to hop out of the train, walk all the way to the back to retrieve it, and then walk to the front of the train again.

Difficulty: Fun Arafa was visiting a science centre to attend a chemistry workshop. She’d received a confirmation email that told her to head to the room number represented by a yellow flask. Can you help Arafa find the right room number?

Difficulty: Tricky Clare and Jeremy just finished a job overseas, on Dough Island. They received the following as payment, in the island’s currency: A $3 coin A $4 coin A $6 note An $8 note and A $9 note. Clare and Jeremy want to share the money so they both get the same number of…

Difficulty: Tricky Gordon is trying to make it big with his Minecraft-themed parody song channel. He spends a lot of time working on each video, and he wants as many views as possible. Gordon’s noticed some patterns with his view numbers:

Difficulty: Tricky Idir was in the bathroom when he noticed that the tiles weren’t all the same shape! Instead, there were two different shapes of tiles.

Difficulty: Tricky Can you take 2 from FIVE and leave 4?

Difficulty: Tricky While out adventuring, Heracles the Hero came across a monstrous, 9-headed Hydra. Without pausing to think, Heracles pulled out his sword and started cutting off the Hydra’s heads. After several minutes of cutting, Heracles realised it was taking ages to remove the heads. Then he remembered something his friend Euripides told him.

Difficulty: Fun Can you add one symbol below to make half a thousand? 5 5 5 5 5

This brainteaser comes from our new book, Puzzles and Projects. This book features some of the best puzzles, hands-on activities, stories and more from Double Helix magazine. Plus, there’s stacks of new content to explore! You can buy a copy on the CSIRO Publishing website, or pick it up from your favourite bookstore!

Difficulty: Tricky Sian is making a big, shiny cube in Minecraft. It will be 10 blocks wide, 10 blocks deep and 10 blocks high. The outer layer of blocks will be made of gold. Everything inside the cube will be made of obsidian. Will Sian need more gold blocks, or more obsidian ones?