If the bat was £1 more than the ball, and the ball was 0.1, then the bat must cost 0.1 + 1 = 1.10, which clearly cannot be the case. It would be 0.5 for the ball. 0.5 + 1 = 1.05. 1.05 +. 05 = 1.10. It's algebra, a known problem with ChatGPT at present. The funny thing is a lot of people make the same reasoning mistake.