Step 2 Objective

Understand a general statement by finding particular examples that match it.


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.

  • Can you draw a different arrangement?
  • How many crossings are there?
  • Now try another arrangement and explain how many crossings.
  • How would you write this down?

"How many crossings? There are one, two, three, four, five crossings"

 

Four lines crossing

"Four lines, four crossings"