Adding and Subtracting Decimals

Contributor: Elephango Editors. Lesson ID: 10948

What's the point of a decimal point besides making addition and subtraction harder? A musical video and some online practice (and some coins) will show you just how easy and practical decimals can be!

categories

Arithmetic, Integers/Rational Numbers and Operations

subject
Math
learning style
Auditory, Visual
personality style
Lion
Grade Level
Intermediate (3-5)
Lesson Type
Quick Query

Lesson Plan - Get It!

Audio:
  • Have you ever watched a high school or college marching band?

The band members have to line up properly, or the show won't work!

Watch the 2013 Ohio State University Marching Band and think about how much hard work goes into making sure each person is in their proper place!

The Ohio State University Marching Band Performs their Hollywood Blockbuster Show from osumbvideo:

Just like a marching band, an equation with decimals needs everyone to line up in the proper place in order for it to work properly!

Adding and subtracting with decimals can be more challenging than adding and subtracting whole numbers. However, with a little practice; you should be able to add and subtract any decimal number!

Watch Math Antics Addition and Subtraction of Decimals, from Michele Cooper, to learn how:

Let's see if you remember how to line up decimals so you can add or subtract them! (You can watch the video again if you're not sure.)

  • If we have the numbers 4.5, 6.93, and 22; how should we line them up?

Which example below is correct:

  A)   4 . 5  
      6 . 9 3
        . 2 2

 

  B)   4 . 5 0
      6 . 9 3
      2 . 2 0

 

  C)   4 . 5 0
      6 . 9 3
    2 2 . 0 0

 

  • Did you get it right?

Good job!

If not, go back and look at it again. Once you have it, keep going!

Now, subtract 6.98 from 25. Which example is correct:

  A)     2 5 . 0
    -   6 . 9 8

 

  B)   2 5 . 0 0
    -   6 . 9 8

 

  C)         2 5
    -   6 . 9 8

 

  • Did you know that was the correct choice?

If so, great job!

If not, go back and look at it again. Remember, we have to add decimal points to whole numbers and zeroes to fill in missing places.

  • Now, are you ready for another challenge?

Last one! Let's line up some bigger numbers: 234.78, 1270.57, and 4.0038

Hint: Put the biggest whole number first, line up by place value, then put in zeroes for the empty places. You can do it!

Which example is correct:

  A) 1 2 7 0 . 5 7 0 0
      2 3 4 . 7 8 0 0
          4 . 0 0 3 8

 

  B) 1 2 7 0 . 5 7    
    2 3 4 . 7 8      
    4 . 0 0 3 8      

 

  C) 1 2 7 0 . 5 7 0 0
    0 2 3 4 7 8 . 0 0
    0 0 0 4 . 0 0 3 8

 

  • Did you get them all correct, even if you had to look back and try again?

Good work!

When you're ready, move on to the Got it? section to get some more practice!

Elephango's Philosophy

We help prepare learners for a future that cannot yet be defined. They must be ready for change, willing to learn and able to think critically. Elephango is designed to create lifelong learners who are ready for that rapidly changing future.