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BrainTwister #61: Mark to mark

Can you solve this week’s logic puzzle? Plus our quick quiz and the answer to last week’s problem

19 February 2025

New Scientist. Science news and long reads from expert journalists, covering developments in science, technology, health and the environment on the website and the magazine.

#61 Mark to mark

Set by Katie Steckles

Given a ruler that you know is 6 units long, with a mark 2 units from one end, it is possible to measure distances of 2, 4 and 6 units between some pair of points (using the mark and the ends of the ruler).

Where could you add a second mark to the ruler that would allow you to measure all lengths from 1 to 6 units?

A ruler 11 units in length has a mark at 1. Where can you add two more marks to allow you to measure 10…

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