Number line

• 1). Set the ruler horizontally on a piece of paper. Draw a line over the top edge of the ruler.
  
  
• 2). Draw a line in the middle of the line and write "0." Make horizontal hash marks -- about a centimeter apart -- down both sides of the line.
  
  
• 3). Write a number at the bottom of each hash mark. On the right from the zero, start with 1 and continue until you run out of hash marks. On the left, start with -1 and continue with negative numbers until you run out of hash marks.
  
  
• 4). Use the number line to do math problems. For example, if the problem is 23-7, you would place your pencil on 23 on the number line and count back 7 hash marks.