Decimals can be hard for students to grasp, especially when they don’t have anything to apply the concept to. Hands-on practice can be key to making lasting connections, for students. One great tactic is to use number lines as a review, so your students can not just put their understanding into practice, but also so they can see how decimals fit together.
How to Get Started
On your overhead projector, chalkboard, or whiteboard, draw a number line with 0 at one end and 10 at the other. Draw marks for 1 – 9 in between, but don’t number them! Ask your students what they think belongs in the spaces between 0 and 10. Once they’ve filled in the numbers and talked about how they knew what belonged there, it’s time to move on.
Decimals – Tenths
Draw a second number line, but this time put 0 on one end at 1 at the other. Draw nine marks in between and ask your students to fill in the blanks. Remind them to use the same reasoning they used for the 0 – 10 number line. It may also help to tell them that they can think about this number line as putting the 0 – 1 part of the first number line “under a magnifying glass.”
If they struggle with how to fill in the number line, guide them through the process of finding the halfway mark – counting in from both sides – and ask them to tell you what number comes halfway between 0 and 1. They may need guidance to move from fractions to decimals, but from there, they should be able to fill in the rest of the line!
Decimals – Hundredths and Thousandths
For hundredths (and after that, for thousandths), simply draw another number line with 0 on one end and 0.1 on the other (0 and 0.01 for thousandths). Insert nine evenly spaced marks in between and ask your students to fill in the blanks. Again, remind them to use the same reasoning they’ve used before, knowing the order that numbers come in and knowing what to call the halfway point.
What Now?
You can expand this activity by pointing out how decimals correspond to the metric system and ask students to look at metric rulers so they can see the similarities. There are also several websites – here and here – where you can go to create decimal number line worksheets for students to practice individually, in small groups, or at home
