I'm sure the answer is simple but my old brain has stopped working. My petrol tank was 25% full. I topped it up to full and it cost me £40. If I had let the tank run empty how much would it cost to fill it up to 100%? I would be grateful if you could explain how you worked it out. thanks in advance
Three quarters of a tank cost you £40. So one quarter of a tank would have cost you a third of that = £13.33. Add that onto the three quarters, to give you a full tank, and you get £53.33.