A Mathematical Mystery
I used my Oyster Card for the first time last Monday (29 September), on a day trip to London. I've had it for about a year, but owing to cirumstances beyond my control I didn't have chance to use it until then. It still had the initial £5.00 credit from when I first ordered it. After checking out the Transport for London website, I decided to put an extra £5.00 onto it to tide me over. I used the TfL website to add a fiver about three weeks ago. I had an email telling me that it was only valid for seven days, and needed to be 'activated' at my nominated station (Earls Court) before it would be added to my balance. If it wasn't activated, it would be automatically refunded to my bank account. Needless to say, I was travelling nine days later. When I arrived in London, I therefore had to put a further five quid onto my card to see me through the day. I made the most of the card, mind you: one tube journey in Zone 1, and five bus journeys in Zones 1 and 2. To put this