Explain what a number line is to students and tell them that number lines can look different. Tell them that a number line starts with the lowest number and that the numbers are in counting order. Show students a number line that only shows the tens numbers. Practice placing the tens numbers on the number line. Ask students to determine which number belongs at the arrow. Next show a number line with the tens numbers, but with shorter lines between the tens numbers. Say that these shorter lines represent one number each. Discuss with students that counting from left to right is counting forwards, and counting right to left is counting backwards. Look to see which tens number the arrow is closest to. Use that to determine if you should count forwards or backwards. Practice together with students with determining which number the arrow is pointing at and by dragging the numbers to their correct positions.

Check that students understand placing numbers to 50 on the number line by asking the following questions:

- What is a number line?

- How do you place a number on the number line?

- Where do you start counting from?

- When do you count forwards and when do you count back?