119, 019, 609, 809, xxx, 909

What is the underlying principle here?

Source: 2.2., 4, https://www.helsinki.fi/sites/default/files/atoms/files/psykologia_valintakoe_2019.pdf


1 Answer 1


The answer is:


You might think I have made a mistake there, but I suggest that you:

consider what all of the terms of your sequence look like when written on a calculator (or similar 7-segment display) and turned upside down!

Try it yourself and see!

  • $\begingroup$ Classic parking place puzzle. Upvote. $\endgroup$
    – z100
    Sep 29, 2020 at 20:06

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