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: