Captain Blackheart buries his treasure but loses his treasure map! But all is not lost. His trusty crew remember different bits of the map.

"I remember drawing it with 5 squares each way", says the Captain.

"There was a row of three trees running due East from the square (1,1)", Peg Leg Pete says. "You put each one of them on a different square."

"Weren’t there four granite boulders going due South from (5,5)?" John asks. "I think you put one of them each in a square too."

"Ah!. Now I remember!" yells the Captain. "I buried the treasure half way between the first rock and the most western tree!"

Where is the treasure?

This is a problem about drawing and interpreting maps but it lays the foundations for graphs and Cartesian geometry that will be important in secondary school and at university.

### Problem

Captain Blackheart buries his treasure but loses his treasure map! But all is not lost. His trusty crew remember different bits of the map.

"I remember drawing it with 5 squares each way", says the Captain.

"There was a row of three trees running due East from the square (1,1)", Peg Leg Pete says. "You put each one of them on a different square."

"Weren’t there four granite boulders going due South from (5,5)?" John asks. "I think you put one of them each in a square too."

"Ah!. Now I remember!" yells the Captain. "I buried the treasure half way between the first rock and the most western tree!"

Where is the treasure?

### Teaching sequence

- Set the scene for the problem. This could be done by displaying a 5x5 grid (burnt at the edges) and telling the class that this is the map that the pirate lost and when it was found no details remained.
- Discuss the details that might be found on a pirates map – landmarks, compass directions (N,S,E,W).
- Pose the problem.
- Brainstorm for ways to solve the problem – (draw, use equipment).
- As the students work on the problem check that they understand the use of grid references and the compass directions.
- Wait until all the students have located the treasure before sharing solutions.

#### Extension to the problem

Write clues for their own treasure map. Post as a challenge for others to solve.

#### Solution

We have put all the information from the story on the map below.

The treasure is in (3,3).