Duration between two given time instances — lesson. Mathematics State Board, Class 6.

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Case I: If the given times are in \(24\)-hour format, you can directly subtract those times and find the duration.

Case II: If the given times are in \(12\)-hour format, first convert them into \(24\)-hour format, and then subtract those times and find the duration.

Example:

1. Calculate the duration between \(10\!:\!40\) hours to \(16\!:\!15\) hours.

Solution:

Starting time \(=\) \(10\!:\!40\) hours

Ending time \(=\) \(16\!:\!15\) hours

Duration \(=\) Ending time \(-\) Starting time

\(=\) \(16\!:\!15\) \(-\) \(10\!:\!40\)

\begin{array}{l} 16 : 15 \\ \underline{- 10 : 40} \end{array}

Here, \(40\) minutes cannot be subtracted from \(15\) minutes.

So, borrow \(1\) hour from \(16\) hours, add this to \(15\) minutes.

\(1\) hour \(+\) \(15\) minutes:

\(=\) \(60\) minutes \(+\) \(15\) minutes

\(=\) \(75\) minutes

Now, subtract \(15\!:\!75\) hours from \(10\!:\!40\) hours.

\begin{array}{l} 15 \underset{\to}{} 75 \\ 16 : 15 \\ - 10 : 40 \\ \bar{\underline{5 : 35}} \end{array}

Therefore, duration between \(10\!:\!40\) hours to \(16\!:\!15\) hours is \(5\) hours \(35\) minutes.

2. Find the duration between \(11\!:\!20\) a.m. to \(5\!:\!30\) p.m.

Solution:

Let us first convert the given times to \(24\)-hour format.

Starting time \(=\) \(11\!:\!20\) a.m. \(=\) \(11\!:\!20\) hours

Ending time \(=\) \(5\!:\!30\) p.m. \(=\) \(5\!:\!30\) \(+\) \(12\!:\!00\) \(=\) \(17\!:\!30\) hours

Duration \(=\) Ending time \(-\) Starting time

\(=\) \(17\!:\!30\) hours \(-\) \(11\!:\!20\) hours

\begin{array}{l} 17 : 30 \\ - 11 : 20 \\ \bar{\underline{6 : 10}} \end{array}

Therefore, the duration between \(11\!:\!20\) a.m. to \(5\!:\!30\) p.m. is \(6\) hours \(10\) minutes.

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7. Duration between two given time instances

Theory: