Did you enter our October brain teaser puzzle? If so, here’s a reminder of the puzzle, and here’s the solution:
I have walked a total of 3,000 metres.
On the way to the pond I walked 500 metres, plus an unknown distance back to my wallet, plus 1,000 metres. On the way back, I walked 1,000 metres minus that same unknown distance to the wallet, plus 500 metres. So the total distance I walked is 500 metres plus 1,000 metres plus 1,000 metres plus 500 metres. The unknown distance is added once and subtracted once, so you can answer the question without needing to know it!
Congratulations if you got it right!