Adding decimals is very similar to adding whole numbers. Our interactive lesson will teach you everything you need to know. Pay special attention to Step 4!
Master adding decimals with place value understanding
Just follow the three rules below in the order they are listed here!
Rule #1
Make sure that the decimal numbers you are adding are like decimals. For example, 2.325 and 4.8 are not like decimals since they do not have the same number of decimal places or the same number of digits to right of the decimal point.
Just add zeros as placeholders until the decimals are like decimals. For example, just add two zeros as placeholders after 8 to get 4.800. Now, 2.325 and 4.800 have the same number of decimal places.
Rule #2
Once the decimals are in vertical format, the most important rule, in my opinion, is to align the decimal points and keep the digits with the same place value in the same column. This will ensure that you do not add tenths to hundredths or hundredths to thousandths and so forth...
Rule #3
If you have done rule #1 and rule #2, you are ready to add digits that have the same place value. Remember to carry numbers when necessary just like you do it when adding whole numbers.
Finally, do not forget to write the decimal point that is located between the digit in the ones place and the digit in the tenths place!
Master the fundamentals of adding decimals through an engaging, visual approach that makes abstract concepts concrete. This interactive tool transforms decimal addition from a memorized procedure into a deeply understood mathematical concept.
For Students
Students benefit from multiple representations of the same concept, reinforcing learning through visual, numerical, and interactive elements. The tool breaks down complex decimal addition into manageable steps, starting with place value understanding and progressing through visual regrouping with colorful base-ten blocks.
Interactive navigation allows students to work at their own pace, clicking through Steps A-D to see how hundredths, tenths, ones, and tens combine and regroup. The "Answer so far" feature shows the running total after each step, helping students understand how the final answer is built progressively. Visual blocks make abstract decimal values tangible—students can literally see 15 hundredths becoming 1 tenth and 5 hundredths.
For Teachers
Teachers gain a powerful demonstration tool that addresses common misconceptions about decimal addition. The place value chart clearly shows why lining up decimal points matters, displaying carries above each column to illustrate regrouping. This visual evidence helps students who struggle with the "why" behind decimal addition rules.
The tool supports differentiated instruction—advanced students can work independently while teachers provide targeted support to those who need it. Use it for whole-class instruction on interactive whiteboards, small group interventions, or independent practice. The step-by-step format allows teachers to pause at any point for discussion or clarification.
Key Features
Perfect for grades 4-6, homeschoolers, and anyone building strong decimal operation foundations.