You are used to teaching repeating decimals with bar notation that keeps us from writing that number over and over again; now teach what the over and over again represents. This activity allows your mathematicians to explore the infinite decimal and see how different calculations get us close to the original number, but not quite exactly on it. The lesson includes commentary and a solution key to help guide the activity. 
Mr. Khan reminds us that the most important thing to remember when subtracting decimal numbers is to line up the decimal points. He subtracts 3.600 from 9.005, explaining his thinking as he completes the process. Assign the viewing of this tutorial as homework and then have youngsters come to class ready to practice together!
A rational number is a ratio of two integers. Discuss with your class how to convert the rational numbers of repeating decimals to fractions. A good commentary on letting x equal the repeating decimal and multiplying each side of such equation by a power of 10 or 10r, where r is the repeating segment.
Multiplying decimal numbers isn't that much different than multiplying whole numbers. If you need a little extra support, this video may help. Sal shows how to multiply 23.12 by 0.5. He takes care to line up the decimal points, regroup, and place the decimal in the proper place when he finishes his computation.
Divide decimals. Watch as Sal explains how to divide 1.03075 by 0.25. He provides a step-by-step process that is easy to follow, clear, and well-organized. Note: This would be great for a teacher prepping for a math lesson or as supplemental material to show in class.
Have your young mathematicians complete this practice problem along with Sal. To solve this thinking problem, they will need to multiply decimal numbers in order to determine the cost of 14.6 gallons of gas when gas costs $2.70 per gallon.
Adding decimal numbers is very similar to adding whole numbers. Sal takes you through the process in this video. First he lines up the decimal points. Then he adds each place value, regrouping when necessary.
Students access prior knowledge of long division and multiplying decimals.  In this dividing decimals lesson, students view a demonstration of how to move decimals when dividing.  Students complete a dividing decimals worksheet. Students compare decimals to fractions.
Practice dividing decimals with your math class. They will review long division skills and review how to move the decimal place during division. Then they complete worksheets to demonstrate their comprehension of this skill.
Students review the relationship between decimals and fractions.  In this rounding decimals lesson plan, students discuss money and how you can round it out to the nearest cents, dollar or ten dollars or hundreds.  Students draw a relationship to other numbers.  Students complete a worksheet.
Sal uses some real life examples to explain percent gain. He also demonstrates how to convert percentages to decimal numbers in order to solve the problems.
Students explore decimals. In this number sense lesson, students view a demonstration of how to write decimals. Students identify the fractions that the decimals represent.
Students identify and write the decimal and fraction represented in a given model. In this fractions and decimals  lesson, students write the numerical equivalent in decimal and fraction form after observing the teacher create a model with various manipulatives. Students complete a related chart.
Students use video clips to help them understand decimal addition and errors in decimal equations. In this decimal addition lesson, students watch and complete several videos about decimal addition. Students also complete two assessment activities of decimal addition.
Learners divide and multiply decimals. In this algebra lesson, students investigate properties of decimals with place holders. They use the correct place holder to multiply and divide decimals.
How can a zero affect place value? After going over the definition of a decimal and reviewing how to convert to a fraction, the whole group works to compare numbers with decimals where the zeros are in different place values. Emphasis is placed on the fact that zeros work differently in decimals than they do in whole numbers. The lesson calls for a supplementary worksheet, but does not include one.
In this decimal vocabulary worksheet, students match a set of 27 words to their correct definitions. Answers are included on page 2; a reference web site is given for additional activities.
Students convert between decimals and ratios. In this algebra lesson, students identify the percent of a number by multiplication. They convert between fractions, percents and decimals.
For this math worksheet, students practice division of decimal numbers by one-digit whole number divisors. Students complete 45 examples written both horizontally and vertically. Problems are spaced close together which may make showing calculations difficult.
In this decimals word search instructional activity, students find a set of 27 decimal vocabulary words in a word search puzzle. A reference web site is given for additional activities.