Multiplying and dividing decimals

Multiplying and dividing decimals

Lesson objectives

Divide integers and decimals by a single-digit number, continuing the division to a specified number of decimal places.

Multiply and divide integers and decimals by decimals such as 0.6 or 0.06, understanding where to place the decimal point by considering equivalent calculations .

Add (+) or Subtract (-) with decimals

• Line up the decimals

• Fill in the empty spots with zero

• Add or subtract

• Bring down the decimal in your answer

Divide by a whole number

To divide into a decimal, you use the same method as with whole numbers.

Sometimes you will need to add extra zeros at the end to complete the division.

Some numbers do not divide exactly and the question asks you to give your answer to a particular degree of accuracy. You should continue dividing until you have one decimal place more than the problem asks for. Then round the answer to the degree of accuracy required

Multiple Choice

What is 63.2 divided by 5?

• 12.63

• 12.87

• 12.64

• 12.65

Multiple Choice

20.2 ÷ 4 = 

• 505
• 0.55
• 50.5
• 5.05

Multiple Choice

Calculate

1.08÷4

• 2.7

• 0.27

• 2.07

• 0.20

Multiplying by a decimal

• Decimals point do not have to line up

• Multiply out the decimal without the decimal point.

• count how many decimal place in the first number

• count how many decimal place in the 2nd number and add with the first

• Those is how many places you move the decimal in your answer

Multiple Choice

305 x 4 is 1220. How much is 3.05 x 0.4?

• 122

• 12.2

• 1.22

• 0.122

Multiple Choice

0.3 x 0.5

• 0.15
• 1.5
• 15
• 150

Dividing by a decimal

• use the method of dividing by 0.1 and 0.01

• For example, to work out 7.8 ÷ 0.06 you can find an equivalent calculation that uses 0.01 instead of 0.06.

• divide by 0.06 you divide by 6 and then by 0.01

• 7.8 ÷ 0.06 = 7.8 ÷ 6 ÷ 0.01

• Dividing by 0.01 gives the same answer as multiplying by 100.

Multiple Choice

4.2 ÷ 0.01 =

• 420
• 42
• 4200
• 0.042

Multiple Choice

2.7 ÷ 0.3 =

• 9
• 90
• 27
• 270

Multiple Choice

1.68 ÷ 0.8

• 2.2
• 2.1
• 2.3
• 2