a train covers its outward journey at 99mph it returns over the same distance at 49.5mph what is the trains average speed over the entire journey?
The MENSA answer is 66 mph Why?
The distance is not relevant, so call it 99 miles.
The outward journey takes 1 hour (99 mikles at 99mph)
The return journey takes 2 hours (99 miles at 49.5 mph)
Total mileage is 198 miles, total time is 3 hours.
Average speed is 198/3 = 66 mph.