This interactivity allows you to sort letters of the alphabet into two groups according to different properties.
On a clock the three hands - the second, minute and hour hands - are on the same axis. How often in a 24 hour day will the second hand be parallel to either of the two other hands?
Investigate the positions of points which have particular x and y coordinates. What do you notice?
How does the position of the line affect the equation of the line? What can you say about the equations of parallel lines?