Take the bus, these days in most places the cost is the same for all journeys, and will be a lot cheaper than £18 for 2 of you (and definitely no need to tip the driver).
Taxi fares marginally decrease per mile over distance, so if the higher bill is £16 for both of you, then it would be fair to pay 50% of the total. This way you BOTH save money.
I think £10 for him and £8 for you - he saves £6 and you save £5. Just splitting it would mean he saves £7 and you only save £4 which is not fair for a long-term arrangement.
Personally I would just split the increased fare down the middle. You're still paying less than what you would if you were on your own so I can't see the issue.
£9 x 2 = £18
£10 x 2 = £20 (If you want to tip/still less than solo journey)
Replies
...only joking!
There's no algebra needed -- just simple fractions.
£9 x 2 = £18
£10 x 2 = £20 (If you want to tip/still less than solo journey)
Depends on what you value more?
I would say split it £8 for the shorter journey and £10 for the longer journey and tip at your discretion ☺