Issue 24
Crossnumber

Prize crossnumber, Issue 24

Can you solve it?

post

13 November 2026

Our original prize crossnumber is featured on pages 58 and 59 of Issue 24.

Rules

  • Each clue in this crossnumber is of the form $a+b$, $a-b$, $a\times b$, or $a\div b$ (where $a$ and $b$ are two positive integers, but the symbols +, –, × and ÷ have each been replaced with a different digit from 1 to 4 (with each symbol always being replaced by the same digit). For example, if × has been replaced with 2 and + has been replaced with 1 then the clue ‘127712’ could represent ‘1×7712’ or ‘1277+2’. In every clue of the form $a-b$, $a$ is larger than $b$ (so the result is not negative). In every clue of the form $a\div b$, $a$ is a multiple of $b$ (so the result is an integer).
  • Ignoring the bars and reading downwards, the digits in the rightmost column reveal one final clue — the answer of this clue can be used to enter the crossnumber competition.
  • There is only one solution to the completed crossnumber. Solvers may wish to use the OEIS, Python, a very large times table poster, etc to (for example) calculate the results of multiplying some large numbers, but no programming should be necessary to solve the puzzle. As usual, no entries begin with 0.
  • One randomly selected correct answer will win a £100 Maths Gear goody bag, including non-transitive dice, a Festival of the Spoken Nerd DVD, and much, much more. Three randomly selected runners up will win a Chalkdust T-shirt. Maths Gear is a website that sells nerdy things worldwide, with free UK shipping.
  • To enter, submit the answer to the clue in the rightmost column using this form by 31 January 2027. Only one entry per person will be accepted. Winners will be notified by email and announced in issue 25.

Crossnumber

Crossnumber #24, set by Humbug:

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