Convert number into time

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I_hate_maths

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I'm kinda embarrassed about this but I need help with a few maths questions which are bound to show up on my exam next week. Here's one such question:

Convert 16315 seconds into hours, minutes and seconds

Here is my current working out:

16315 divided by 60 =271.916666667 (for hours)
271.916666667 divided by 60 =4.53194444444 (for minutes) etc

The frustrating thing is that on the answer sheet it jumps from 4.53194444444 to hrs=4:31:55 and I don't know that can be right. So I'm feeling kinda dumb but this question is worth a good 2 points and I know that it's something I should be able to answer. Help?
 
I_hate_maths said:
I'm kinda embarrassed about this but I need help with a few maths questions which are bound to show up on my exam next week. Here's one such question:

Convert 16315 seconds into hours, minutes and seconds

Here is my current working out:

16315 divided by 60 =271.916666667 (for hours)
271.916666667 divided by 60 =4.53194444444 (for minutes) etc

The frustrating thing is that on the answer sheet it jumps from 4.53194444444 to hrs=4:31:55 and I don't know that can be right. So I'm feeling kinda dumb but this question is worth a good 2 points and I know that it's something I should be able to answer. Help?
Click to expand...

16315 seconds = 271 minutes and 55 seconds

271 minutes = 4 hours and 31 minutes

16315 seconds = 4 hours and 31 minutes and 55 seconds
 
Instead of writing the quotient as a long decimal fraction, it would be better to leave it as "integer quotient and remainder". 60 divides into 16315, 271 times with a remainder of 55 so 16315 seconds is 271 minutes and 55 seconds. 60 divides into 271 4 times with a remainder of 31 so 271 minutes is 4 hours and 31 minutes.
 
Subhotosh Khan said:
16315 seconds = 271 minutes and 55 seconds

271 minutes = 4 hours and 31 minutes

16315 seconds = 4 hours and 31 minutes and 55 seconds
Click to expand...

I'm still confused. If I divide 16315 by 60 the answer is 271.916666667 then what do I divide the number by? Cos if I divide it again by 60 I get 4.53194444445 which is obviously incorrect.
 
HallsofIvy said:
Instead of writing the quotient as a long decimal fraction, it would be better to leave it as "integer quotient and remainder". 60 divides into 16315, 271 times with a remainder of 55 so 16315 seconds is 271 minutes and 55 seconds. 60 divides into 271 4 times with a remainder of 31 so 271 minutes is 4 hours and 31 minutes.
Click to expand...

I get dividing it by 60 but how did you get a remainder of 55? I'm not seeing it on my calculator at all.
 
I_hate_maths said:
I get dividing it by 60 but how did you get a remainder of 55? I'm not seeing it on my calculator at all.
Click to expand...

That's the difference between dividing with "paper and pencil" and dividing with calculator (some calculators can give you remainders - most don't).

You can also find in the following way:

16315 / 60 = 271.9166667

Remainder is 0.916667*60 = 55
 
On your calculator, after getting 16315 / 60 = 271.9166667, subtract 271 (the integer part), press "=", and then multiply by 60.
 
Ok so basically it's 16315 divided by 60 = 271.916666667. Then I ignore 271 for the moment and instead write the number as 0.916666667. From there we multiple it 0.916666667 *60 =55.0000002. Now I have 271 for the minutes and 55 for the seconds

Then what do I do to find the exact hours? Just make an estimate? Like 60 can go into 271 4 times so therefor the answer is 4hrs? And the remainder 31 becomes the minutes. Or is there a better way of doing it?

Lol I think I've kinda did this in a very backwards way.
 
Last edited:
I_hate_maths said:
Ok so basically it's 16315 divided by 60 = 271.916666667. Then I ignore 271 for the moment and instead write the number as 0.916666667. From there we multiple it 0.916666667 *60 =55.0000002.
Click to expand...
The "2" at the end is an artifact of that "7" you got by rounding up. Obviously, 16315 divided by 60 is 271 plus an integer remainder. As a check, 271*60= 16260 so that 271*60+ 55= 16260+ 55= 16315.

Now I have 271 for the minutes and 55 for the seconds

Then what do I do to find the exact hours? Just make an estimate? Like 60 can go into 271 4 times so therefor the answer is 4hrs? And the remainder 31 becomes the minutes. Or is there a better way of doing it?

Lol I think I've kinda did this in a very backwards way.
Click to expand...
What you have done is correct. 271= 60(4)+ 31. 271 is 4 hours and 31 minutes. 16315 seconds is 4 hours, 31 minutes, and 55 seconds.
 
I_hate_maths said:
I'm still confused. If I divide 16315 by 60 the answer is 271.916666667 then what do I divide the number by? Cos if I divide it again by 60 I get 4.53194444445 which is correct but in the wrong form.
Click to expand...

4.53194444445 hrs = 4 hrs + 0.53194444445 hrs
0.53194444445 hrs = 60 * 0.53194444445 min = 31.916666667 min = 31 min + 0.916666667 min
0.916666667 min = 60 * 0.916666667 min = 55 sec

So, 4:31:55 in the correct form. It might be easier though to do it the interger-remainder way.
 
Last edited:
Ishuda said:
4.53194444445 hrs = 4 hrs + 0.53194444445 hrs
0.53194444445 hrs = 60 * 0.53194444445 min = 31.916666667 min = 31 min + 0.916666667 min
0.916666667 min = 60 * 0.916666667 min = 55 sec

So, 4:31:55 in the correct form. It might be easier though to do it the interger-remainder way.
Click to expand...

Cool. Anyway I tried the same method for another question and my answer was close but it was of by 1:

Convert 13955 seconds into hours, minutes and seconds.

13955/60=232.583333333 [232 minutes]
0.583333333*60=34.999999998 [34 seconds]

Estimate: 232/60=3
60*3=180
232-180=52

My answer =3hrs 52 mins 34 sec or 3:52:34

However the correct answer was 3:52:35. I assume that this was just rounded up to the nearest five for some reason?
 
You should round off that number
0.583333333*60=34.999999998
which, rounded to the nearest integer second, is 35 sec.

If you do the round off at the end to the accuracy you are initially given, you will generally get the correct answer, depending on the accuracy of your calculator/computer.
 
HallsofIvy said:
Better would be to be able to do division without a calculator!
Click to expand...


Yes, I agree but I think the key there is "be able to do division without a calculator", not necessarily to do division without a calculator.

Edit: But then is always that 'use it or lose it' bub-a-boo hanging around.
 
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