Can you solve this puzzle?

It is a hot moonless night. A Yowie (cousin of Big Foot) can be heard in the distance.

Four bushies (people living in the Australian outback) are standing on the west bank of the Murray River. They decide to cross the rickety wooden bridge over the river before the Yowie gets there.

You have only 17 minutes to get all of the bushies across to safety on the other side before the Yowie gets there. (The Yowie is too heavy to cross the bridge.) 

The bridge is old and they must cross carefully to avoid the gaping holes and fall through to the churning river below. They only have one torch (flashlight) to light the way in the dark.

The bridge can only support a maximum of two people crossing at one time.

Any man who crosses, either 1 or 2 at a time, must have the torch with them or risk drowning. They decide that the torch must be walked back and forth over the bridge. They cannot risk throwing it and losing it in the river.

Each bushie walks at a different speed. When two men walk across the bridge, they walk together at the rate of the slower man’s pace.

Wally takes 1 minute to cross the bridge.
Bluie takes 2 minutes to cross the bridge.
Redmond takes 5 minutes to cross the bridge.
Stropy takes 10 minutes to cross the bridge.

Hint
If Wally and Stropy walk across first, 10 minutes have passed when they get to the other side of the bridge. If Stropy returns with the torch, a total of 20 minutes have passed, and you have failed the mission.

Answer

Did you figure out how to solve it ?  No?

Let’s review how the men walk:

Wally takes 1 minute to cross the bridge.
Bluie takes 2 minutes to cross the bridge.
Redmond takes 5 minutes to cross the bridge.
Stropy takes 10 minutes to cross the bridge.

Now the Answer

Wally and Bluie travel over the bridge first and Bluie brings back the torch taking 4 minutes.

Then Redmond and Stropy travel over and Wally brings back the torch taking 11 minutes.

Finally Wally and Bluie travel over the bridge taking 2 minutes. Everyone has travelled safely over the bridge in only 17 minutes. 

The Yowie arrives on the west bank just as the last of the bushies reaches the east bank. He sighs sadly and starts eating the yowies he’s brought to share with the men. (Yowies are also chocolate candy bars made by Cadbury and loved by Aussie kids young and old alike).

If you like Yowies, you’ll like the Cadbury Yowie website. It’s the official website of the Yowie Kingdom, and your source for the latest Yowie news, Yowie fun and cool Yowie Stuff.