If you ever had to simulate random outcomes in excel sheet, you might have already heard of about the spreadsheet function rand(), this little function generates a random fraction between 0 and 1 whenever you use it. So I usually write = if I need a random number between 0 to 12. Of course, if you have analysis tool pack installed like I do, then we can use round(rand()*12,0)int(rand()*12)+1randbetween(0,12) to do the same.
In order to simulate a dice throw, thus you can use round(rand()*5,0)int(rand()*6)+1
So, what would you do if you need to simulate the face total when you throw 2 dice?
round(rand()*10,0)int(rand()*11)+2
Wrong
Why? Apparently a random number between 2 and 12 (1 is not possible as the minimum you can get when you throw two dice is 2) doesn’t simulate 2 dice throws properly.
The CORRECT way to do this is instead generate 2 individual random numbers and add them up, like:
round(rand()*5,0)int(rand()*6) + 1 + round(rand()*5,0)int(rand()*6) + 1
Here is why this is correct way to simulate dice throws using random number generator functions:
I have ran these 2 random functions each for 2500 times and plotted the distribution:
As you can see, the left plot of int(rand()*11)+2 tells that each of the 11 possibilities (2,3,4,5,6,7,8,9,10,11) are equally likely. But that is not what happens when you throw a dice, you see an awful lot more 5,6,7,8 than you see a perfect 12 or 2. And there is a reason for that, the distribution of 2 dice throws is actually a bell curve, and when you use int(rand()*6) + int(rand()*6) + 2 the distribution is bell curvish.
Update: Thanks to Jon for pointing out that round() is not the choice if you want random integers, you should use int instead. See his explanation in the comments and the illustration here.
I have used this logic to simulate monopoly board game and prove that it is not really that random.
More on games: Bingo / Housie ticket generator excel sheet
13 Responses to “Convert fractional Excel time to hours & minutes [Quick tip]”
Hi Purna..
Again a great tip.. Its a great way to convert Fractional Time..
By the way.. Excel has two great and rarely used formula..
=DOLLARFR(7.8,60) and =DOLLARDE(7.48,60)
basically US Account person uses those to convert some currency denomination.. and we can use it to convert Year(i.e 3.11 Year = 3 year 11 month) and Week(6.5 week = 6 week 5 days), in the same manner...
This doesn't work for me. When applying the custom format of [h]:mm to 7.8 I get 187:12
Any ideas why?
@Jason
7.8 in Excel talk means 7.8 days
=7.8*24
=187.2 Hrs
=187 Hrs 12 Mins
If you follow Chandoo's instructions you will see that he divides the 7.8 by 24 to get it to a fraction of a day
Simple, assuming the fractional time is in cell A1,
Use below steps to convert it to hours & minutes:
1. In the target cell, write =A1/24
2. Select the target cell and press CTRL+1 to format it (you can also right click and select format cells)
3. Select Custom from “Number” tab and enter the code [h]:mm
4. Done!
Hi, sorry to point this out but Column C Header is misspelt 'Hours Palyed'
good one
So how do I go the other way and get hours and minutes to fractional time?
If you have 7.5 in cell A1,
- Use int(A1) to get the hours.
- Use mod(A1,1)*60 to get minutes.
If you have 7:30 (formatted as time) in A1
- Use hours(a1) to get hours
- Use minutes(a1) to get minutes.
I had the same issue. You can solve it by changing the format as described above:
Right click cell > Format Cells > (In Number tab) > Custom > Then enter the code [h]:mm
([hh]:mm and [hhh]:mm are nice too if you want to show leading zeros)
Thanks guys, these are the tips I'm looking for.
...dividing the number of minutes elapsed by the percent change is my task - "int" is the key this time
It doesnt work for greater than 24 hours
It returns 1:30 for 25.5 hours. It should have returned 25:30
Ideally I would right function as
=QUOTIENT(A1,1)&":"&MOD(A1,1)*60
Sorry, replied to wrong comment....
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I had the same issue. You can solve it by changing the format as described above:
Right click cell > Format Cells > (In Number tab) > Custom > Then enter the code [h]:mm
([hh]:mm and [hhh]:mm are nice too if you want to show leading zeros)
Clever use of MOD here to extract the decimal part of a number. Divide a number containing a decimal by 1 and return the remainder. Humm. Very clever.
Thanks very much, extremely useful !