1. Each take a sheet as in the previous games and tell your partner the number of your
chosen ship.
2. In this game you can find out which column (0 to 9) the ship is in. You simply add
together the digits of the ship’s number. The last digit of the sum is the column the ship is
in. For example, to locate a ship numbered 2345, add the digits 2+3+4+5, giving 14. The
last digit of the sum is 4, so that ship must be in column 4. Once you know the column
you need to guess which of the ships in that column is the desired one. This technique is
called ‘hashing’, because the digits are being squashed up (“hashed”) together.
3. Now play the game using this new searching strategy. You may like to play more than
one game using the same sheet—just choose from different columns.
(Note that, unlike the other games, the spare sheets 3A' and 3B' must be used as a pair,
because the pattern of ships in columns must correspond.)