River Crossing Puzzle Solutions

Watch the fewest-trip answer to all 11 puzzles, one crossing at a time, with a tip for each type.

Wolf, goat and cabbage: bring the goat back (7 trips)

The goat can’t be left with the wolf or the cabbage. So bring the goat back with you.

Fox, chicken and grain (or corn) is the same riddle with the same answer. See it ›

Two adults, two children: the children bring the boat back (9 trips)

The two children cross and one comes back. Then an adult crosses alone.

A child on the far bank brings the boat back, so it takes 4 trips to move each adult. See it ›

Bridge and torch in 17 minutes: send the two slowest together

First the two fastest cross, so one can row back. Then the two slowest cross together.

Time for 4 people who take 1, 2, 5 and 10 minutes

For the two slowest people (Y and Z), take the faster of these two ways:

• The two fastest (A and B) help, and Y and Z cross together: A + 2B + Z minutes
• The fastest (A) takes each one across: 2A + Y + Z minutes

Repeat from the slowest down. The last two cross together; with three, A takes each one.

This also solves 5 people in 29 minutes and the daily puzzle. See the 17-minute answer ›

Missionaries and cannibals (sheep and wolves): gather the wolves first

A bank with only wolves never breaks the rule.

So first gather the wolves on the far bank, then take the sheep over two at a time.

11 trips at best. The key is trip 6: a sheep and a wolf row back. See it ›

3 parents, 3 children: children first

A bank with only children never breaks the rule.

So first gather the children on the far bank, then the parents cross two at a time.

11 trips at best. The key is trip 6: a parent and their own child row back. See it ›

Family (police officer and thief): the thief moves with the officer

This is the family puzzle often shared online as a “Japanese IQ test”.

• The thief moves only with the officer, or waits alone on a bank with no family
• Move the family in safe pairs: Dad and a son, Dad and Mom, Mom and a daughter

17 trips at best. The key is trip 4: the officer and the thief row back. See it ›

FAQ

Can the boat cross empty?

No. Someone has to row, even on the way back.

How are trips counted?

Each crossing counts as one, there or back.

Is there only one answer?

Not always. Wolf, goat and cabbage has 2: you can swap the wolf and the cabbage.

Can 4 people cross in under 17 minutes?

No. Checking every way to cross shows 17 minutes is the fastest.

Is the bridge and torch puzzle the same?

Yes. The torch (or flashlight) has to be carried back, just like the boat.

Missionaries and cannibals solution?

11 trips, the same as 3 sheep and 3 wolves (the sheep are the missionaries).

What is the answer to the daily puzzle?

Tap “Solve” in the game, or work it out with the method above.

Where are the answers to the hard puzzles?

In the diagram above: pick one under “Hard”.