Back in the day Lord Swanning-Freeloader was going to attend a lunch and summoned his chauffeur with the car. "Take me to The Jolly Quizmaster and go at 30 miles per hour" he instructed.
The chauffeur replied that he had checked on a map, and had worked out that they would arrive half an hour early if he drove at 30 miles per hour.
"I can't be early, so go at 20 miles per hour. It will be more comfortable on the rough roads in any case" his lordship suggested.
The chauffeur responded that this would indeed be more comfortable, but would cause them to be half an hour late.
Somewhat exasperated the peer of the realm told the driver to go at the speed which got them there on time.
How fast did the chauffeur drive?
It is possible to work out the distance using simultaneous equations, but a quick examination should reveal that they are going to travel 60 miles. At 30 miles per hour it will take two hours and at 20 miles per hour it will take three hours - the one hour difference in time suggested.
His lordship wants the journey to take two and a half hours, which needs a speed of 24 miles per hour.