Step 9 Objective

Represent problems and synthesise information in algebraic, geometric or graphical form; move from one form of presentation to another to gain a different perspective on the problem/task.


What if pupils find this a barrier?

diagram showing three lines crossing

Line Crossings

  • Draw three straight lines (line segments) so that some cross over each other.
  • How many crossings are there?
  • Try different arrangements of the lines. What is the maximum number of possible crossings?
  • Try using more lines.
  • Is there a rule for the maximum for any number of lines? If so, write it down.

Use the problem Line Crossings.

Look at your table of results:

  • Can you explain a rule for finding the number of intersections for any number of lines?
  • How would you write this down?