word problem

[elizabethz]

an animal trainer wants to move 2 lions and a monkeyto another training area.He can move only one animal at a time. He cannot leave the monkey alone with either lion. How many trips will he have to make?

 

[elizabethz]

This is an ancient puzzle, usually told involving a wolf, a goat and a cabbage. A monkey is more appealing than a cabbage so I like this version.

The puzzle really needs only logic to solve, no math.

Here is a hint: remember that on some trips he can have NO animals. So some trips have one animal and some have none. So the puzzle reduces to how to move the animals around so that whatever two animals are left together are lions.

Thank you for taking the time to help. Your hint was made it all very clear!