# Guess my number

ES1 – A thinking mathematically context for practise exploring comparative relationships between numbers to 10

## Syllabus

Syllabus outcomes and content descriptors from Mathematics K–10 Syllabus © NSW Education Standards Authority (NESA) for and on behalf of the Crown in right of the State of New South Wales, 2023

• MAO-WM-01
• MAE-RWN-01
• MAE-RWN-02

## Collect resources

You will need:

• numeral cards 1-10 (optional)

• building blocks

• pencils or markers

## Watch

Watch Guess my number video (2:09).

Guess a number using only 'greater than' or 'less than' as clues.

### Transcript of Guess my number video

(Duration: 2 minutes 9 seconds)

Hi Sarah.

Hi Holly.

### Holly

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

[Screen shows cards from the number 1 to 8 in a row. Above the cards are blocks that represent the amount of the numbers on the cards.]

### Sarah

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

Guess my number!

### Sarah

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.

### Holly

Yeah. So which number should I choose?

[Screen shows Holly with the deck on cards fanning them out to select one card.]

Alright. I choose this one....

[Holly selects a card with number 4.]

### Sarah

Are you showing everybody at home?

[Holly shows her selected card to everyone at home.]

Oh, don't peek.

I'm not peeking.

### Holly

Alright, you can go now.

OK.

### Holly

What is my number?

Is it, 3?

Higher.

### Sarah

It is higher than 3.

### Holly

So, can it be 1 or 2?

### Sarah

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

[Sarah removes cards and towers for one and 2.]

### Holly

It can't be 3 either.

[Holly removes card 3 and tower.]

### Sarah

You're right because you said it was higher than 3. OK, so I only get 3 guesses. Is that right?

OK, so I've used up one guess alright. OK. Is the number 7.

No. Lower.

### Sarah

Oh, it's lower than 7.

### Holly

It can't be 8 and it can't be 7.

[Holly removes card and towers for 7 and 8.]

### Sarah

OK, so it's 4, 5 and 6.

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

### Holly

Ding ding ding ding!

### Sarah

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.

[End of transcript]

## 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.

## Reflection

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

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