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Triangular Numbers

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pinkee | 21:43 Sat 15th Jul 2023 | Quizzes & Puzzles
9 Answers
Struggling with this one. Can anyone help please?


Rearrange the numbers 1 to 10 so that the addition of every adjacent pair of numbers is a triangle number.
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You mean the total of each adjacent pair is a triangular number?
10-5-1-9-6-4-2-8-7-3
The triangle numbers are 1 3 6 10 15 (then 21 but thats to big)
good one jonathonjoe, your to fast for me
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Yes, I think that's what it means
Yours even meets the other rule that not only do first and second got to add up to a triangle number, but the second and third, then 3rd and 4th and so on
is it cheating to allso say 3 7 8 2 4 6 9 1 5 10
Question Author
Thank you both. Jonathan-Joe - that's what I was looking for!
Just to say, those are the only solutions -- though, if you throw in 11 as well, you can find two unique ones:

11 10 5 1 9 6 4 2 8 7 3
and
9 6 4 11 10 5 1 2 8 7 3

Looks like it gets more fun when you add 12 as well (for, perhaps, a loose definition of "fun").

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