The Tunnel

This puzzler is mathematical in nature. It is not automotive, but it does involve a train.

Two children are walking along a railroad track. (Don't try this at home people...)

It is a single railroad track. They enter a tunnel and they begin walking along the single track inside the tunnel. A very dangerous thing to do.

When they get to the point that is 2/5ths of the way into the tunnel, they hear the train coming behind them. They hear the train whistle.

There is no escape or exit, other than the beginning or the end of the tunnel. One the children begin running toward the train, back the way they came. They were only 2/5ths of the way in, so he goes that way. The other kid runs towards the end of the tunnel, the other 3/5ths of the way, away from the train.

They are both running at 15 miles per hour. So one kid runs toward the train. The other kid runs away from the train. And they just make it.

The puzzler is, how fast was the train going?

Now, you'll notice I left out some key pieces of information. How long is the tunnel? How far away is the train? You don't have that info.

Good luck.

Answer the Puzzler »

Remember last week's puzzler?

The Ripcord

Okay, here it is. On my street, a few of the neighbors and I communally own a big Acme Leaf Thrasher, a big leaf sucker machine. This thing reduces 400 bushels of leaves into like a teacup. For yard maintenance.

This thing sucks up all the leaves, and anything else in its path, for that matter.

Now, it's a great device but it was way too expensive for one individual to buy. Four of us got together and we bought this thing communally and I was assigned the task of maintenance.

So there we were and the fall season was over, and we had to put this thing to rest, only to be fired up again next fall. All our leaves were taken care of for the season, so I decided to take care of the machine. The neighbors were all watching. They love to watch me work because I'm the only one in the neighborhood that isn't retired.

So, I did all the usual stuff. I put some gasoline stabilizers in the gas tank and I changed the oil and all that. I took the spark plugs out and I put a couple of squirts of motor oil and I yanked on that cord a few times to splash that stuff around.

And then I very slowly pulled the cord until I reached what I knew was the critical position of the ripcord. And then I stopped. And one of my neighbors says "Why are you doing that?

So, that is this week's puzzler. Why did I pull the ripcord all the way out to the critical position?