In this activity, we will be learning how to use estimates and rounding when calculating times.

 

In real life, it is very useful to be able to work out roughly how long it takes for something to happen, or the actual time when something will take place. Often, an estimated time is useful because units of time like minutes are relatively short. 
 

Remember that there are 60 minutes in an hour.

Half an hour is 30 minutes.

A quarter of an hour is 15 minutes. 

 

In this activity, it will help to round times to the nearest whole, half or quarter of an hour. 

 

For example:
5:06 is closer to 5 o'clock than to quarter past 5. 
5:28 is nearly half past 5, or 5:30.

 

Let's try some examples, so you know how to approach this activity.

 

Example 1

A football match lasts for 1½ hours.

It starts at 4:28 p.m.

Roughly, when will it finish?

 

Answer

The first step here is to round the time given to the nearest half hour. 

4:28 is nearly 4.30, which is much easier to deal with.  

Count on half an hour to 5.00

Now, count on an hour to 6.00

The match will finish at approximately 6.00

 

 

Example 2

I set my alarm clock for 6:03 tomorrow morning.

I go to bed at 10 o'clock at night.

Roughly, how many hours sleep could I get?

 

Answer

Firstly, let's round the time we need to get up to 6.00 This makes the time easier to work with. 

Next, count the hours from 10 o'clock at night, to 6 o'clock the next morning.

11, 12, 1, 2, 3, 4, 5, 6

This means that the answer is approximately 8 hours of sleep.

 

Let's have a go at some questions now.