Decimal Operations Lessons

Decimal Operations

Adding, Subtracting, Multiplying and Dividing Decimals

Adding Decimals

To add decimals start by writing the amounts out and lining them up by the decimal points.

Multiple Choice

Try this:

$$42.46\ +\ 10.44$$  

• 529

• 52.9

• 52.80

Subtracting Decimals

Subtracting decimals is similar to adding decimals. When subtracting decimals you are going to write out the two pieces to the problem by lining up the decimal points.

Things to remember

• We line up the numbers by their decimal points to make sure they are in the correct place value when adding/subtracting

• When adding be sure you are regrouping when needed

• When subtracting be sure you are borrowing when needed

Multiple Choice

Try this:

$$5.18\ -\ 2.30$$  

• 2.28

• 2.88

Multiplying Decimals

• When you multiply decimals you do not line up the problem by the decimal points

• Starting from the right side of each number, count how many decimal places you have with each number

• Multiply as you usually would, starting from the right and working to the left

• Write down the amount of decimal places there are to the right of. the problem and circle it

Multiplying decimals

• After you finish multiplying, add up the decimal spaces from each part of the problem

• Then go to the product and count from right to left to find the placement of your decimal

• 
  

• 
  

Multiple Choice

Try this:

$$5.05\ \times\ 3.1$$  

• 1.5655

• 156.55

• 15.655

Dividing Decimals

• Start by identifying the dividend and the divisor in your problem

• Rewrite the division problem using the division house with the dividend under the "house"

• Divide normally (think of how many times the divisor will go into the dividend)

• Bring up the decimal point into the quotient

Multiple Choice

Try this:

$$8.5\ \div5$$  

• 1.7

• 17