**Learning Objective:**

Name multi-digit numbers, use previous information to solve problems.

**Intended Outcome:**

Using previous information to eliminate digit possibilities.

**Materials:**

- Whiteboard
- Pen and paper

**Game Objective:**

To guess the mystery number.

**Instructions:**

This game is to be played as a whole class, in small groups or in pairs.

- The ‘caller’ decides a mystery number. Four or more digits is best.

Hint: Write the mystery number down; relying on memory is hard. - A player guesses the number and the guess is written on the board.

Hint: It is a good idea for the teacher to do the writing as it makes it faster. - The caller marks each digit of the number with a tick if it is correct, a circle if it is in the mystery number but not in the correct place, and a cross if it is not in the number at all.
- Players continue guessing and the caller continues marking each digit in each number, until the correct number is discovered.
- Ensure the students name the number correctly aloud, e.g. Forty-three thousand, seven hundred and eighty-six.

**Example:**

Hidden mystery number: 49273

First guess:

4 3 7 8 6

✓ o o x x

Second guess:

4 1 9 3 2

✓ x o o o

Third guess:

4 9 2 3 5

✓✓✓ o x

Fourth guess:

4 9 2 7 3

✓✓✓✓✓

**Variation:**

Try using decimals in the mystery number.

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