Decimal number lines can be a great tool to teach students the basics of decimal numbers. It can help them understand the concept of place value, as well as visualizing and comparing different decimal numbers. Here are some activities that can be used to teach students decimal number lines:

1. Introduction to Decimal Number Lines: Start by introducing students to the concept of decimal numbers and what they represent. Explain how we use decimals to represent fractions or portions of a whole number. Show them how decimals are marked on a number line and how they can be compared to other numbers.

2. Interactive Number Line: Use an interactive whiteboard or a number line app to create a digital number line. Have students drag and drop decimal numbers onto the line and order them from smallest to largest. This will help them understand the placement of decimals on a number line.

3. Fraction to Decimal Conversion: Convert fractions to decimals and plot them on a number line. For instance, convert 1/2 to 0.5 and plot it on the number line. Ask students to identify equivalent fractions and plot them on the same number line.

4. Ordering Numbers: Provide students with a set of decimal numbers and ask them to order them on a number line from smallest to largest. This activity will help them understand the value of each decimal place in a decimal number.

5. Adding and Subtracting Decimals: Use a number line to teach students how to add and subtract decimals. Model examples and ask students to practice using the number line to visualize the addition and subtraction process.

6. Decimal Race: Create a game where students race to plot decimals on a number line accurately. This fun activity can help build accuracy and speed in identifying decimal numbers on a number line.

7. Round to the Nearest Decimal: Teach students how to round decimals to the nearest whole number or decimal place. Have them plot the rounded number on the number line and compare it with the original decimal value.

In conclusion, learning decimals can be challenging, but using a number line can make it much easier and engaging for students. These activities can help students master the basics of decimal numbers and build their confidence in working with decimal numbers.