Money- Warm up-by Rob Vingerhoets

Task 1: HOW MUCH MONEY IS IN MY POCKET?
Students have 8 questions to ask in order to work out how much money is in the pocket. The 9th turn is a
guess of the amount.
Only one questions can be asked per person.
Clearly mark down the side of the whiteboard the numbers 1 – 9, but place a dotted line between 4 and 5,
7 and 8, and 8 and 9. These dotted lines indicate pauses.
Determine your starting range: $0 – $500
The only answers that can be given to the student questions are: Yes/No.
Do the thinking out aloud for the students and discuss the relationships.
Eg: make the connections 50% which is the same as 0.5 which can also be expressed as ½.
Pause the game after question 4. Delete any of the information that is now superfluous due to the new
range.
After you have given your response to Question 7, then list all of the numbers which are available as
potential answers. The students need to have 15 or less options to proceed to Question 8.
Example below: (This is the task we were given and we still do not know the amount of money that was in
the pocket.)
Question Response
1
2
3
4
—————
5
6
7
—————
8
—————
9 – Guess the value!
The questions the audience asked were: Responses
1. Is the value less than $250? Yes
2. Is the value an even number? No
3. Is the value less than or equal to $99? Yes
4. Are there any coins in the pocket? Yes – but no decimals. (Extra hint given here)
Now go back and look at the questions. Which ones are now unnecessary? You can delete question 1 and
the response. This does NOT mean an extra question is given to the students.
The audience continued with these questions: Responses
5. Is the value a multiple of 3? No
6. Is there the digit ‘9’ in the value? No
7. Is there more than 10 coins? No
Now go back and look at all of the possible remaining answers. Remember: if there are more than 15 the
game stops. 1, 5, 7, 11, 13, 17, 23, 25, 29, 31, 35, 37, 41, 43, 47, 53, … and the list continues.
THIS GAME STOPS!!!!