Topics
8. Time
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Australia
Year 5

8.03 Passing time

Lesson
Practice

Are you ready?

Can you convert between seconds, minutes and hours?

Examples

Example 1

How many minutes are there in 2 hours?

Worked Solution
Create a strategy

Use the fact that there are 60 minutes in 1 hour.

Apply the idea

Converting 2 hours into minutes, we have

\displaystyle 2 \text{ hours}\displaystyle =\displaystyle 60 \times 2Multiply 60 by 2
\displaystyle =\displaystyle 120 \text{ minutes}
Idea summary

There are 60 seconds in 1 minute.

There are 60 minutes in 1 hour.

Passing time

This video looks at calculating passing time in minutes, hours and seconds.

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Examples

Example 2

Find the value of 5 hours 10 minutes - \, 2 hours 40 minutes.

Worked Solution
Create a strategy

Use a vertical algorithm and the conversion 1 \text{ hour}= 60 \text{ minutes}.

Apply the idea

To subtract the times, we can write it in a vertical algorithm. Make sure to align the hours, colon and minutes.\begin{array}{c} & &5 & : &10 \\ &- &2 & : & 40 \\ \hline & \\ \hline \end{array}

Since 10 minutes is less than 40 minutes, we trade 60 minutes from 5 hours.

So, we have 10+60=70 minutes in the first row and 5 hours becomes 4 hours.\begin{array}{c} & &4 & : &70 \\ &- &2 & : & 40 \\ \hline & \\ \hline \end{array}

Subtracting each column, we have:\begin{array}{c} & &4 & : &70 \\ &- &2 & : & 40 \\ \hline & &2&:&30 \\ \hline \end{array}

The difference is 2 hours and 30 minutes.

Idea summary

We can use subtraction to find the difference between times, but we have to be careful when we need to regroup and remember:

\displaystyle 1 \text{ hour}\displaystyle =\displaystyle 60 \text{ minutes}
\displaystyle 1 \text{ minute}\displaystyle =\displaystyle 60 \text{ seconds}

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