Download Mystery Number!

Mystery Number!
Learning target: develop number sense and mental math agility
Supplies: small white boards
Instructions for facilitator:
1.
2.
Give students three clues and ask them to figure out the number.
For instance: I’m thinking of an odd number between 5 and 15. The number has 2 digits. The two
digits are the same. What’s the number?
3.
Second round: I’m thinking of an even number between 2 and 12. The number has 1 digit. Half of the
number is 3. What’s the number?
4.
Third round: I’m thinking of an odd number between 7 and 19. The number has 2 digits. It can be
divided into three equal groups. What’s the number?
5.
Fourth round: I’m thinking of an even number between 0 and 5. The number has 1 digit. It is a prime
number. What’s the number? (You will get a chance to introduce prime numbers on this one.)
6.
Fifth round: I’m thinking of an even number between 20 and 30. The number has 2 digits. Half of this
number is one dozen. What’s the number?
Extensions:
1.
2.
3.
Introduce prime and composite numbers to add more clues.
Negative numbers would add an interesting element.
Use squares and cubes as clues.
Submitted by: Carol Eldon