The Great Number Hunt (Sorted)

Steps

1. Ask: is it easier to find a book in a library if the books are in alphabetical order?
2. Pairs sit back to back with a sheet of 31 sorted boxes.
3. One partner picks a number that the other must find. Guess the middle box first.
4. After each guess, the partner says higher or lower. Discard half the boxes every time.
5. Count guesses and add them to the class chart.
6. Compare this chart with the unsorted one.

Talk about it

• How many guesses did it take at most?
• Why is guessing the middle smart?
• Could this work for billions of items?