Problems from Express and operate with time in hours, minutes and seconds

Let's calculate:

$(5 h 3^{'} 34^{″}) - (1 h 35^{'} 21^{″})$
$(6 h 7^{'} 55^{″}) \cdot 5$

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Development:

1. Since the minutes to subtract $(35)$ are bigger than those that we have $(3)$ we must subtract one hour from the original time and add $60$ minutes to the minutes of this first time. This leads us to the operation to be calculated as:

$(4 h 63^{'} 34^{″}) - (1 h 35^{'} 21^{″})$

Once we have the expressed the operation like this, we proceed to subtract each of the factors separately and we have:

$3 h 28^{'} 13^{″}$

2. We multiply every factor by $5$ and we get: $30 h 35^{'} 275^{″}$

Since we have more than $60$ seconds, we convert them into minutes. We divide $275$ by $60$ . We take the integer part.

$\frac{275}{60} = 4, 5833$

We multiply the integer part $4$ by $60$ and we subtract it from $275$ original. We get:

$4 \cdot 60 = 240 \Rightarrow 275 - 240 = 35$

Therefore, we must add $4$ more minutes to the result and leave only $35$ seconds. This is: $30 h 39^{'} 35^{″}$

Solution:

$3 h 28^{'} 13^{″}$
$30 h 39^{'} 35^{″}$

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