A relative of mine (who shall remain nameless) was deeply perturbed one day over an accountancy problem. Seeing her in a spot of bother I asked what was up. "I can't figure this one out" she said, "I've been putting 50 euros a month into the bank for the last year and I seem to be 100 short. But I KNOW the money went into the bank!" She proceeded to demonstrate, counting on her fingers - "look, 50 euros, and 50 euros and 50 euros..." and so on until we arrived at 500 euros instead of the expected 600. "A year, you say?" I asked, she nodded "and since when did you have 12 fingers?" I continued. The good news is that once I said it she immediately got the point and almost p****d herself laughing.