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Grade 5

Converting units of time


Some of the units we use to measure time are hours, minutes and seconds.  In Converting between hours, minutes and seconds, we saw how to convert between different units of time.

$1$1 Week $=$= $7$7 Days
$1$1 Day $=$= $24$24 Hours
$1$1 Hour $=$= $60$60 Minutes
$1$1 Minute $=$= $60$60 Seconds

 We can use multiplication and division to convert between different units of time.  

Example 1

If it took $9$9 hours and $15$15 minutes to drive to Sydney, how many minutes did it take?  

Think: Firstly calculate how many minutes are in $9$9 hours.  

We know that $1$1 hour  = $60$60 minutes, so to calculate the number of minutes in 9 hours we need to multiply

$9$9 x $60$60 = $9$9 x $6$6 tens = $54$54 tens = $540$540 minutes

So there are $540$540 minutes in $9$9 hours.

Next we need to add $540$540 minutes and $15$15 minutes

Do: Calculate $540$540 + $15$15 

One way to make this calculation easier is to think of $15$15 = $10$10 + $5$5

Adding $540$540 + $10$10 + $5$5 = $555$555

So it took $555$555 minutes to drive to Sydney.


Don't forget to write the units.

Worked Examples

Question 1

How many hours are there in $600$600 minutes?

Question 2

A phone call takes $120$120 seconds.

How many minutes does the call last?


Maximilian ran a marathon in $2$2 hours and $42$42 minutes.

How many minutes was this?

We work with time in almost every area of our life, so knowing how to add time, calculate the time between events, or even use a 24 hour clock are important.   Let's look at some common ways we may need to work with time.  

Solving different types of time problems

In the first video, you'll see how to calculate elapsed time, how to add two blocks of time together, as well as how to work out how long you might need to binge-watch your favourite tv show!


Sometimes you may need to know how to use 24 hour time, so this video shows you how to do that. It's only a short video, showing you how you can add or subtract 12, to move between the 12 and 24 hour clock.

Worked Examples

Question 1

Find the value of

$3$3 hours $3$3 minutes $+$+ $3$3 hours $29$29 minutes

  1. $\editable{}$ hours $\editable{}$ minutes

Question 2

A song clip starts playing at $7$7:$55$55 pm and finished at $8$8:$11$11 pm. How long is the song clip in minutes?

Question 3

Amy wants to re-watch every episode of her favourite TV show to prepare for a trivia contest. Each episode is $30$30 minutes long and there are $12$12 episodes.

  1. How many minutes will it take Amy to watch every episode again?

  2. How many hours will it take?




Estimate, measure (i.e., using an analogue clock), and represent time intervals to the nearest second

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