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7.04 Passing time


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Can you add and subtract minutes to a designated time? Try this one.


Example 1

Taylan's piano lesson went from 11\text:15 until midday.

A clock where the small hand is passed 11 and the long hand is pointing at 3.

How many minutes was Taylan's lesson?

Worked Solution
Create a strategy

Midday is another word for noon. At this time both hands would be pointing at 12.

So we need to find the number of minutes between 3 on the clock and 12.

Apply the idea

The minutes hand points at 3 which means 15. When the minutes hand points at 12 it means 60 minutes.

So we need to find 60-15 by using the vertical algorithm:

\begin{aligned} &&6&0 \\ &-&1&5 \\ \hline \\ \hline \end{aligned}To subtract the 5 in the ones column we must borrow from 6: \begin{aligned} &&5\text{}^1 &0 \\ &-&1&5 \\ \hline && 4&5 \\ \hline \end{aligned}Taylan's lesson is 45 minutes.

Idea summary

The number of minutes must be between 0 and 60. If we go below this, then we are counting backwards into the previous hour. If we go over this, then we are counting forwards into the next hour.

Passing time in minutes and hours

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

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Example 2

Find the value of: 3 hours 3 minutes + \, 3 hours 29 minutes

Worked Solution
Create a strategy

Add the minutes and hours separately.

Apply the idea
\displaystyle 3+29\displaystyle =\displaystyle 32Add the minutes
\displaystyle 3+3\displaystyle =\displaystyle 6Add the hours

So there are 6 hours 32 minutes.

Idea summary

When adding and subtracting times, add or subtract the minutes and hours separately. Keep in mind that there are 60 minutes in 1 hour.

It can be easier to count up from one time to another, rather than try to perform a complex subtraction.



reads and records time in one-minute intervals and converts between hours, minutes and seconds

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