**Change between time units** *KS2 Revision*

## What you need to know

**Things to remember:**

- There are 60 seconds in 1 minute
- There are 60 minutes in 1 hour
- Write the question as a sum to calculate. When converting from minutes into hours this means writing it as a fraction with 60 as the denominator.

We know that:

There are 60 seconds in 1 minute

There are 60 minutes in 1 hour

Now, let’s try converting between some units of time.

What is \frac{1}{2} of an hour in minutes.

*Remember: **There are 30 minutes in half an hour, so let’s see if that is what we get here.*

We know that an hour is 60 minutes, so we need to find \frac{1}{2} of 60 minutes. But, we know that finding half of something is the same as dividing by 2.

\frac{1}{2}\text{ of }60 = 60\div2 = 30

So, half on an hour is 30 minutes, as you should know.

What about if we want to turn minutes into hours? Well, we do this with fractions!

What is 15 minutes in hours?

*Remember: **15 minutes is the same as quarter of an hour, so let’s see if that is what we get here.*

To convert into hours, we divide the minutes we have by 60. We divide by 60, because there are 60 minutes in one hour!

*Remember: **We can write division questions as a fraction.*

15\div60=\frac{15}{60}

But, this doesn’t really help us much, so let’s simplify this fraction down.

\frac{15}{60}=\frac{1}{4}

So, we can see that 15 minutes is the same as quarter of an hour, as we’d expect!

## Example Questions

**Question 1:** What is \dfrac{1}{4} of 3 hours?

1 hour = 60 minutes

2 hours = 120 minutes

3 hours = 180 minutes

To find \dfrac{1}{4} we divide by 4.

180\div4=45

\frac{1}{4} of 3 hours is 45 minutes.

**Question 2:** What is 150 minutes in hours?

150\div60=\frac{150}{60}

\frac{150}{60}=\frac{15}{6}

We know how to convert improper fractions into mixed numbers:

}=2\frac{3}{6}=2\frac{1}{2}

150 minutes is the same as 2 and a half hours.