The Bridge of Tom and Ray

May 28, 2011

RAY: In Borneo, there is a bridge connecting two islands. It is constructed of bamboo, lashed together with hemp, and it's been used for hundreds of years. The bridge is four miles long and it has a weight limit of 20 tons.

One day, a truck full of sedated pigs pulls up to the bridge, ready to cross. The officials stop him and say, "We have to weigh you."

Once on the scale, the truck weighs *exactly* 20 tons. The bridge is emptied. The driver is allowed to drive across the bridge.

As he drives across, a sparrow begins to follow alongside. Just when he's beyond the halfway point, the sparrow lands on the truck.

What does the driver do to keep the truck and the sedated pigs from plunging into the abyss? (Note: jumping out of the cab and into the abyss is not an option.)
 
Answer: 
RAY: Here's the answer. The truck driver could do a lot of things to keep from plunging into the abyss. For example, figuring that his shoe weighs more than a sparrow, he could throw a shoe out the window. But he needn't do anything.

TOM: Wow!

RAY: It's a trick question, what does he do? He does nothing, because in driving from the beginning of the bridge to the halfway point a 20-ton truck is going to consume fuel.

TOM: Oh!
RAY: And it'll easily consume an amount of fuel that's greater than the weight of the sparrow, so when the sparrow lands on the truck, nothing happens. Do we have a winner?

TOM: The winner is Dave May, from Cedar Falls, Iowa. Congratulations Dave!

Get the Car Talk Newsletter