Decimals
NZ Level 5
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Divide numbers with tenths by a single digit number
Lesson

Why do we need to divide decimals?

Sometimes, before you can really understand how to perform some number problems, it helps to understand why you need to do them. In the video below, we will look at why you may need to solve a problem such as $13.2$13.2 divided by $4$4.

Let's say there are $4$4 students, and the teacher has $13.2$13.2 hours available throughout the term to provide some extra help with their reading. This division problem can help work out how much each child will be allocated. The answer, in this case $3.3$3.3 hours each, can then be converted to hours and minutes. We won't solve that part here, but you can see how knowing how to solve the division part of this is useful. Oh, by the way, if you want to work on your time problems, you can click here to do that!

Let's work through some similar examples now in the video. Thinking about tenths is really important, as we are looking at whole numbers and decimals.

 

Now we’ll look at using short division as a way to solve a division with decimals. Short division has less steps than long division, as you do some of the mental maths in your head as you go, which we work through here in Video 2. In this example though, we need to rename some of our digits, just like we would when dividing whole numbers.

Remember!

We use the same approach we use for whole numbers, it's just that we work on places to the right of our decimal point, in this case, tenths.

Examples

Question 1

We want to find $99.3\div3$99.3÷​3. We are going to do this by first partitioning the number.

  1. Break up $99.3$99.3 into a sum of tens, units and tenths. Use whole numbers or decimals.

  2. To find $99.3\div3$99.3÷​3 we can divide each of $90$90, $9$9, and $0.3$0.3 by $3$3 and add the results together.

    Answer the following. Give each answer as a whole number or a decimal.

    $90\div3=\editable{}$90÷​3=

    $9\div3=\editable{}$9÷​3=

    $0.3\div3=\editable{}$0.3÷​3=

  3. Hence, what is $99.3\div3$99.3÷​3? Write your answer as a decimal.

QUESTION 2

We want to find $67.4\div2$67.4÷​2

  1. Choose the most reasonable estimate for $67.4\div2$67.4÷​2

    $34$34

    A

    $3.4$3.4

    B

    $340$340

    C

    $0.34$0.34

    D

    $34$34

    A

    $3.4$3.4

    B

    $340$340

    C

    $0.34$0.34

    D
  2. Complete the short division to find $67.4\div2$67.4÷​2

      $\editable{}$ $\editable{}$ $.$. $\editable{}$
    $2$2   $6$6 $7$7 $.$. $\editable{}$ $4$4
     

QUESTION 3

We want to find $264.5\div5$264.5÷​5

  1. Choose the most reasonable estimate for $264.5\div5$264.5÷​5

    $53$53

    A

    $530$530

    B

    $5.3$5.3

    C

    $0.53$0.53

    D

    $53$53

    A

    $530$530

    B

    $5.3$5.3

    C

    $0.53$0.53

    D
  2. Complete the short division to find $264.5\div5$264.5÷​5

        $\editable{}$ $\editable{}$ $.$. $\editable{}$
    $5$5   $2$2 $6$6 $\editable{}$ $4$4 $.$. $\editable{}$ $5$5
       

Outcomes

NA5-3

Understand operations on fractions, decimals, percentages, and integers

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