Question

Subtract and write out in minutes and seconds 87 seconds from 100 seconds

Answer 1

Answer:

  00:13  mm:ss

Step-by-step explanation:

There are 60 seconds in a minute. This fact can be used to convert the time period(s) to minutes and seconds either before or after you do the subtraction.

Difference

It is often convenient to do arithmetic with all of the numbers having the same units. Here, we are given two values in seconds and asked for their difference.

  100 s - 87 s = (100 -87) s = 13 s

The difference between the two time periods is 0 minutes and 13 seconds.

Conversion

If you like, the numbers can be converted to minutes and seconds before the subtraction. Since there are 60 seconds in a minute, the number of minutes is found by dividing seconds by 60. The remainder is the number of seconds that will be added to the time in minutes:

  87 seconds = ⌊87/60⌋ minutes + (87 mod 60) seconds

  = 1 minute 27 seconds

  100 seconds = ⌊100/60⌋ minutes + (100 mod 60) seconds

  = 1 minute 40 seconds

Then the difference is found in the same way we would find a difference involving different variables. (A unit can be treated as though it were a variable.)

  (1 min 40 s) -(1 min 27 s) = (1 -1 min) + (40-27 s) = 0 min 13 s

The difference between the two time periods is 0 minutes and 13 seconds.