Bubblecar said:

The Rev Dodgson said:

dv said:

Okay, you’ve both writtled to the right answer which Bubblecar gave mere seconds after seeing the puzzle.

A mere 675 seconds, to be precise.

Yes, it did require a bit of working out :)

Thanks to dv for a teaser that actually needed some thinking about :) (the New Scientist ones have been way to easy recently).