Working out average speeds

Booldawg | 08:18 Tue 13th Jun 2006 | How it Works

8 Answers

Maths isnt my strong point! Whats the formula for working out average speeds in MPH? For example; I cycle to work, its 3.2 miles and I did it in 12mins 25 secs. How would I work out the average mph for the journey?

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tellboy

Its the hour (60minutes) dived by the time taken (12.25 min) times the distance isnt it ?

tellboy

try again ! divided !

or distance (miles) /time(hr) =mph

Booldawg

Question Author

thanks tellboy

Kerplunk

To get the time in hours you would do 745 (no. of seconds it took you) divided by 3600 (number of seconds on an hour) this gives 0.2 approx. Next you would divide 3.2 by 0.2 to give you the average speed in mph. It is about 16 mph.

halfadaily

with a calculator I've got 12 mins 25 secs = 12.4166 mins divided by 3.2 miles = 3.88 mins.

60 mins divided by 3.88 = 15.463 mph

I think that's how you do it !

Booldawg

Question Author

all three formulaes are giving results quite close to each other. I'm not quite sure if my cycles computer has a function to calculate average speeds as its fairly user unfriendly and i've not got a manual for it! I may flick through the functions and see if i get any readings close to what I've worked out on the calulator!

fo3nix

speed is, as you say, miles per hour.

whenever you see the word "per", remember that it means "divide". so speed is miles divided by hours, or not in terms of the units:

speed = distance / time

now, you want the speed in miles per hour. you already have your distance in units of miles, so that's ok. but your time is in minutes and seconds: you want it in hours.

so, to turn 25 seconds into minutes first, we do 25/60 (60 seconds in a minute), to get 0.416 minutes. this feels about right if you think about it: 0.5 minutes is half a minute which would be 30 seconds, so 0.416 is just under 30 seconds, in fact 25 seconds!

so, adding this time in minutes to the 12 minutes that you quote, we have a time of 12.416 minutes. now, we want this time in hours, and since there's 60 minutes in an hour, we divide it by 60 to get a time of 0.20694 hours.

now, we have units in hours and miles as you want, so can just use the formula above to find out the speed:

speed = distance / time
speed = 3.2 / 0.20694
speed = 15.46 mph

doglady

Can I just compliment fo3nix on their excellent explanation of how to work that out.

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