A commuter is in the habit of arriving at his suburban station each evening at exactly five o’clock. His wife always meets the train and drives him home. One day he takes an earlier train and arrives at his station at four o’clock. The weather is pleasant so instead of telephoning home, he starts walking along the route always taken by his wife. They meet somewhere along the way.
He gets into the car and they drive home arriving ten minutes earlier than they usually do. Assuming that the wife always drives with a constant speed, and on this particular occasion she left just in time to meet the five o’clock train, can you determine how long the husband walked before he was picked up?
Source: My Best Mathematical and Logic Puzzles, by Martin Gardner; Puzzle #8
Target Ages: All ages
Alok Goyal's Puzzles Page 
55 min
Hi Alok,
Should be 55 minutes..
Assuming the wife usually travels an hour daily, she must leave at 4.30 to pick her husband and both reach back home at 5.30. On this ocassion they returned home 10 mins early, i.e. at 5.20, which means the wife travelled for 50 mins both ways. That would mean the husband walked for 25 minutes.
One of my favorites. It begs for more data but yet has such a simple solution …
Agreed. I tried this puzzle in February, and initially wandered around quite a bit and in the end realized that the solution was rather simple and felt very stupid!
i also was trying with some equations, then felt, for equations need more data … bt at times its one simple hint – which make it work! The constant speed did the trick for me…
another good one…
He walked for 1 hour and 5 minutes.
He walked for 1 hour and 5 mins.
Thanks, but it is not the correct answer
5 minutes
Thanks Rajeev, not the right answer. Just posting the answer!