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Play a game of Salvo!

By David Shaw, 10 January 2013

Here’s a fun game to play, but there’s more to it than chance. Have a try, then see if you can use some maths strategies to improve your game!

You will need

• Someone to play against
• Two copies of the target sheet – you can download the sheet here
• Pencils

Draw your ships into the larger grid.

What to do

1. Look at the target sheet. There are two grids and five types of vessel. Without your opponent seeing, draw one of each vessel anywhere on the largest grid. They can be placed running up and down or left and right. They can’t overlap each other, and they aren’t allowed to fall off the edge of the grid. The largest one is five boxes long and one box wide, and the smallest is two boxes long and one box wide.
2. Once you have both placed your fleets, take turns firing. Take care to keep your map hidden from your opponent’s view. Use the smallest grid to keep track of your attacks.
   

   When you make a shot mark the hit or miss on the smaller grid.

If you are firing

1. Choose a square that you want to fire at on the small grid.
2. Find the letter above and the number to the left of your chosen square.
3. Call out the letter and number to your opponent.
4. Wait for your opponent’s reply.
5. If they say ‘miss’, mark the square with a single diagonal on the small grid.
6. If they say ‘hit’, mark it with a cross.

If your opponent is firing

1. Find the letter and number they call out on the large grid.
2. Mark the box that is in that column and row.
3. If part of your ship is in that box, say ‘hit’.
4. If there is no ship in that box, say ‘miss’.
   

   When the opponent has hit all the boxes of one of your ships, tell them which one they just sank.

5. When every box of one of your ships is hit, that ship is sunk. Tell your opponent what type of ship it was.

The end of the game

If you sink all your opponent’s ships, you win! If your opponent sinks all your ships, you lose.

What’s happening?

Salvo is a game of communication. It’s important that you and your opponent mark exactly the same box each time a shot is made. The letters and numbers on the columns and rows give each square a unique name, so you don’t get confused. There’s only one square in column D and row 6.

If you manage to sink all your opponent’s ships, you win!

The letters and numbers are called coordinates. Coordinates are used when you need to find something on a grid of boxes. They are often used on maps, to make streets and landmarks easier to find, but they can also be used on other grids. A computer screen is a grid of coloured lights called pixels. Computer programmers can send instructions to individual pixels by naming their coordinates.

Strategies

At first, this game seems to be a game of chance, with no skill at all. However, there are a few strategies you can use to get an advantage.

Firstly, some squares are more likely to have a ship on them than others. There are only two ways to put the smallest boat in the top left corner square – pointing down, or pointing right. There are four different ways of putting it on most of the other squares – pointing up, down, left or right. There are only two ways of putting the longest boat in each corner, but ten ways of covering a given central square!

In order to hit every boat, you don’t need to look at every square. If you imagine the grid is a chessboard, every boat will be on at least one black and at least one white square. So you only need to look at the white squares to find all the boats. You’ll still need to hit some black squares to sink them, though.

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