Lesson: Decimal Addition and Subtraction

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Lesson Objective

Add and subtract decimal numbers

Lesson Plan



6NSO.C8 – Select and use appropriate operations to solve problems involving addition, subtraction, multiplication, division, and positive integer exponents with whole numbers and with positive fractions, mixed numbers, decimals and percents.

6NSO.C10 – Accurately and efficiently add, subtract, multiply and divide (with multi-digit divisors) whole numbers and positive decimals


Key Points

·         Add and subtract decimal numbers

·         We need to line up our place values to add and subtract numbers

·         We can line up our decimals to help us line them up

·         The decimal is the right of a whole number

·         We should add zeros as place holders when our numbers do not line up  (don’ t have the same number of decimal places)


7 + 8.3 + 32.38


1.       Last year, Jenna’s town recycled 9.85 tons of paper. This year, her town recycled 18.5 tons of paper.  How much more paper did the town recycle this year than last year?


A.      8.00 tons

B.      8.65 tons

C.      8.75 tons

D.      9.35 tons 


Darrin’s best time in the hundred-meter dash this season is 13.25 seconds. At the beginning of the season, Darrin’s first run in the hundred-meter dash was 14.6 seconds.  How much did his time improve in the hundred-meter dash?



·         Review fraction computation

·         Discuss that we are going to be reviewing adding/subtracting decimal numbers

·         Have students solve a whole number addition and subtraction problem

·         Highlight how students line up their place values naturally and link to the new learning


Intro to NM:

·         Walk through lining up decimals/place values when the numbers have the same number of decimal places

·         Discuss that sometimes the numbers in the problem don’t have the same number of decimal places

·         In this case we still need to line up our decimals but we should add zeros to serve as place holders so that we do not compute incorrectly

·         Discuss that sometimes a number does not have a visible decimal (whole numbers).  Highlight that in whole numbers the decimal is ALWAYS to the right of the that number.


Guided Practice:

·         Students practice identifying problems that are written correctly vertically

·         Students practice writing whole numbers as decimal numbers

·         Students practice filling zeros in for place holders


Independent Practice:

·         Worksheet



Lesson Resources

CW Add Subtract Decimals   Classwork
HW Unit 5 Add Subtract Decimals  
U6 L8 Smooth Operator add subtract decimals  


Buzz Alcott Posted 2 years ago:

I want to a nice resource where students can practice math.


It works pretty good fpr my kids.



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