Lesson video

Hello, my name is Miss Parnham.

In this lesson, we're going to be learning how to divide a fraction by an integer.

Here we have an example of five eighths divided by three.

So let's draw a diagram.

Here we have five eighths shaded, and we're going to divide that into three equal sections.

And just identifying that section, that gives us five twenty fourths.

And notice this gives us exactly the same answer as five eighths multiplied by one third.

So using that, lets solve another problem, negative four ninths divided by seven, that will give us the same answer as negative four ninths.

Multiply by one seventh, which is negative four over sixty three.

And again, We have two sevenths divided by negative six.

This is the same as two sevenths multiplied by negative one sixth, which is negative two over forty two.

Now that will simplify to negative one over twenty one.

What's about negative five twelfths divided by negative nine? Well, this is the same as negative five twelfths multiplied by negative one ninth, which is five over one hundred and ninth.

Here are some questions for you to try.

Pause the video to complete the task and restart the video when you're finished.

Here are the answers.

If you prefer, you can cancel common factors instead of simplifying in the last step.

So for example, part C, we have four ninths divided by eight which is four ninths multiplied by one eighth.

Let's go ahead and cancel the common factor of four, from the numerator and denominator.

That gives us one over nine multiplied by 201 eighteenth.

Here is another question for you to try, Pause the video to complete the task and restart the video when you're finished.

Here are the answers.

It's probably more difficult when an integer is unknown in these situations, but maybe equivalent fractions might help.

So for example, we have five twenty fourths divided by something is one forty eighths.

Well, you can think of five twenty fourths as ten forty eighths.

So ten forty eighths divided by 10 gives us one forty eighths.

Now we're going to divide a mixed number by an integer.

So we can rewrite two and seven tenths as twenty seven tenths.

and dividing by three, gives us the same answer as multiplying by a third.

So here we have twenty seven multiplied by one over ten multiplied by three, and twenty seven thirteenth will simplify because they're both multiples of three.

So the final simplified answer is nine tenths.

Let's look at an example where one number is negative.

So we can rewrite negative four and seven eighths as negative thirty nine eighths, and we're dividing by six which is the same as multiplying by one sixth.

So we have negative thirty nine multiplied by one over eight multiplied by six.

This gives us negative thirty nine over forty eighth.

And these are both in the three times table so we can simplify further, and we have negative thirteen sixteenths as our final answer.

What he thought of the numbers are negative? Let's rewrite the mixed number as an improper fraction.

So negative four and seven twelfths is negative fifty five twelfths.

And we're divided by negative five, but this is the same as multiplying by negative one fifth.

So this gives us fifty five over sixty, which simplifies to eleven twelfths.

Here are some questions for you to try.

Pause the video to complete the task and restart the video when you're finished.

Here are the answers.

Cancelling common factors, may help you get to an answer quicker.

So for example, part D, we have sixty four fifteenths divided by eight.

That's sixty four fifteenths multiplied by one eighth.

So if we cancel eight from numerator and denominator, we have eight over fifteenth.

Some more questions for you to try.

Pause the video to complete the task.

Let me start the video when you're finished.

Here are the answers.

Did you notice that to work out the side length on the equilateral triangle, you're obviously dividing by three.

And to work it out on the regular hexagon, we're dividing by six.

So once you were confident with your answer for the collateral triangle of three and a half centimetres, then you could divide that by two, to get the side length on the regular hexagon.

And that's one and three quarter centimetres.

That's all for this lesson.

Thank you for watching.