Mathematical Problem Solving

Knot Theory Problem

(a personal favorite)

What Each Student Will Need:

1 plastic milk bottle top
1 pair of scissors.
1 ball of wool or string.

Teacher Step for Safety:

1. Drill 2 holes into each plastic milk bottle top as shown.

Teacher Step to Take Away Clues for Solving the Puzzle:

2. Loop about 30cm of wool through the milk bottle top and tie it with a firm knot.

 

3. Tie the wool and milk bottle top to the handle of a pair of safety scissors as shown here.

 

The Puzzle

Remove the string loop from the scissors without bending anything, cutting the string or undoing the knot. Once you get it off show the teacher and then put it back on. N.B. This is a logical thinking puzzle, not a brute force one.

Just for Fun:

– The children are only allowed to use their scissors when they solve the puzzle 🙂

Things to Remember:

– This is ‘problem-solving NOT problem showing‘. Do not show the solution to your friends no matter how much they beg as you will take the a-ha feeling away from them.
– When they do show their friends how to do it (and they will) discuss how it is funny how no one got the solution and then all at once heaps of people did 😉
– Discuss taking the ‘a-ha feeling’ like a whole group.