Dealing with time and its calculation can be a bit tricky sometimes.
There are the hours, the minutes and the seconds to handle.
We can add or subtract them.
We do not operate in the hundreds, or ones, like any simple arithmetric.
We are calculating in terms of sixties.
1 hour = 60 minutes
1 minute = 60 seconds
Hence when given a maths question on subtracting two times, how do we go about to avoid mistakes?
Let's take an example to illustrate.
John start his journey to the market at 09:15am. If he arrived at the market at 10:05am, how long did he travelled?
We can use the conventional method of carrying back 60 to the minutes, since the ending minute is smaller than the starting minute. And reducing the 10 to 9 (hour).
Next, we can then subtract with the new numbers.
That is 9:65 - 9:15 = 50 minutes.
This answer is fine.
Change all the times to mintes.
10:05 ==> (10 x 60) + 5 = 605
09:15 ==> ( 9 x 60) + 15 = 555
Subtracting the two new numbers gives 50 minutes directly.
And that is the answer!
Comparing approach 1 with approach 2, you would notice that the latter seems to be simpler.
This is because we have simplified the mixture of hours and minutes to only one dimension, that is, the minutes.
Thus, subtracting the newly created numbers involved only the minutes, avoiding the distraction of handling the hours.
To do maths, clear the mind of the unnecessary.
In the example above, we have removed the "hours" factor to focus purely on the "minutes".
Maths is interesting in that it is up to us to "play" with the techniques.
We can work with it or go against it.
The choice is up to us to select.
Hope you pick up some tips to make maths interesting.