One person picks a number and asks the other to double it.
- Round 1: You can start off easy by asking double 3, 9, 12, 15, 35.
- Round 2: Then make it harder 18, 34, 56, 73.
- Round 3: Double and then add 5
- Round 4: Double then subtract 3
Next try taking 1/2 (half)
- Round 5: What is 1/2 of 8, 10, 20, 24?
- Round 6: What is half of 36, 40, 68, 84?
- Round 7: What is half of 56, 74, 96, 104?
- Round 8: What is 1/2 of 35, 41, 73, 87?