Guess My Numbarrrr
How it works
You've been captured by pirates! They're about to make you walk the plank, but first, they offer you a challenge:
- The pirate captain will choose a secret number between 1 and 15, and you will have to try to guess what it is.
- If you guess their secret number before your 4th wrong guess, they will let you go free.
- But if you guess wrong 4 times, you will have to walk the plank.
- After each wrong guess, they will tell you whether their secret number is higher or lower than the number you guessed.
Can you find a strategy you can use that allows you to guarantee that you guess their number correctly, without getting lucky? What if their number is between 1-20? 1-30? 1-50? 1-100? For each of these ranges, how many wrong guesses do you need to be allowed to make in order to guarantee you guess the number?
In this activity, students work together to figure out how to guess a facilitator's secret number. To start, the range is 1-15 and they have to walk the plank after 4 wrong guesses, and their goal is to find a way to guarantee that they can guess the secret number every time, without getting lucky. They also explore larger ranges (1-20, 1-30, etc.).
Why we like this activity
- It's fun! Students enjoy playing the game and figuring out how to beat the facilitator.
- It helps to develop algorithmic and numerical reasoning.
It requires students to engage in mathematical habits of mind:
Using logic and finding and using strategies to guess the number without getting lucky.
Looking for patterns and making and testing predictions when exploring the number of wrong guesses you need to be allowed to make for different ranges.
- It has a low floor and a high ceiling: Students can start playing by trial and error, but figuring out how to guarantee you guess the number correctly before running out of guesses is more challenging!
