Guess my number

Watch the video to learn how to play

Transcript

Hi Sarah.

Hi Holly.

So this time I'm going to... You're gonna guess which number I've got.

OK, sounds like fun. What's this game called again?

Guess my number! OK, alright, so maybe I'll close my eyes where you choose and you can show everybody who's watching the number that you chose.

Yeah. So which number should I choose? Alright.. I choose this one....

Are you showing everybody at home?

Oh, don't peek.

I'm not peeking.

Alright, you can go now.

OK.

What is my number?

Is it, 3?

Higher.

It is higher than 3.

So can it be 1 or 2?

No it can't be Holly, so I'm going to take away one.

It can't be 3 either.

You're right because you said it was higher than 3. OK, so I only get three guesses. Is that right? OK, so I've used up one guess alright. OK. Is the number 7.

No. Lower.

Oh, it's lower than 7.

It can't be 8 and it can't be 7. OK, so it's 4, 5 and 6.

Alright, I've got one more guess. OK. Is the lucky number 4?

Ding ding ding ding!

Yay. Thanks Holly, thanks for playing with me. I wonder if some other people would like to play this game and maybe they could even do numbers larger than eight. What if it was one to 20? I wonder how hard that would be?

Alright, signing out mathematicians.

Collect resources

You will need:

  • numeral cards 1-10 (optional)

  • LEGO or blocks

  • pencils or markers

  • your mathematics workbook.

Instructions

  • Write the numbers from 1 to 10 (for example) on a piece of paper or use cards to set the number range. For example, this student chose to use the numbers between 1 and 8.

  • Ask someone at home (the ‘secret holder’) to choose a secret number within your given range.

  • Guess the ‘secret' holder’s number.

  • They will tell you whether their number is greater or less than your guess.

  • Try to guess the secret number in the fewest number of guesses possible, or, with only 3 guesses.

Uno cards 1-8 on the floor with corresponding amount of Lego blocks placed above the cards.

Reflection

  • What is an effective strategy to guess the number quickly?

  • If you played the game again tomorrow, what would you do differently? Why?

Share/submit

Share your work with your class on your digital platform.

You may like to:​

  • share your responses to the reflection questions

  • write comments​

  • share pictures of your work​

  • comment on the work of others.

Advice for parents

Here is part of a conversation to help illustrate what the game can sound like. This was a game between a teacher and a student, using the number range 1-12.

Secret holder: Ok, make your first guess!

Student: 3.

Secret holder: My number is not 3. But my number is greater than 3. Are there any numbers you can cross off your list?

Student: It’s not 3 so I can cross that off.

Student: It’s not 2 or 1 either as they are less than 3.

Secret holder: That’s great reasoning- because my number is greater than 3, but those numbers are less than 3, they can be crossed off. What is your next guess?

Student: 7.

Secret holder: My number is not 7, but my number is less than 7. Can you cross any more numbers off the list?

Student: Yes! 7...8, 9, 10, 11 and 12!

Secret holder: What are the options you have left?

Student: 4, 5 or 6!

Secret holder: Take some time to think about what a good number would be to guess now.

Student: Maybe 5?

Secret holder: Why do you think that?

Student: If I choose 5...it’s in the middle. So, I will know the answer whatever happens with bigger and smaller. And it could just be 5!