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Maths Nerds......

Cook$

Just the tip....
Jul 7, 2001
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I go out for a run. I run at 10 mph on the way out, then 12 mph on the way back. What is my average speed?
 

jahlad

Emortal
Feb 11, 2002
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assuming its a trick question then 12 miles per hour.
you state you go 'out' for a run and do 10 miles per hour on the way 'out'
once you are 'out' you are already on your way back so do your run entirely at 12 miles per hour

or if its not a trick question and assuming that by 'out' and 'back' you are referring to running to and from a fixed point returning to the same start point then 11 miles per hour
 

Tom

Tom
Nov 27, 2006
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It's not necessary to know the distance or time taken, we know the time going and the time returning, distance is the same either way

10mph and 12mph, or 22 mp 2h
Divide by 2 hours = 11mph
(Note is 'per hour' not 'in an hour', only 10 miles are run back, in less than an hour - but the actual time and distance are still irrelevant)

10 mph is the same as 10 mp 60mins
12 mph is the same as 12 mp 60mins
1 mp 6 mins, 1 mp 5 mins
2 mp 11 mins = 10 mp 55 mins
We need to add 5 minutes for 'per hour'
1 mile would be 5.5 mins (or 5:30)

Shocker - it's not 11mph but 10 point something
 

Cook$

Just the tip....
Jul 7, 2001
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I get it to 10.9 mph.

Lets chuck some numbers in. Say I run 10 miles out, at 10mph. Thats 10 mile in 60 mins, 6 min miles
Then back at 12mph. So 10 mile at 12mph gives 5 min miles. So 50 mins.
60mins + 50 mins =110mins
Ran 20 miles in 110 mins
S = d/t = 20/110 = 0.1818 miles per min
x 60 = 10.9mph
 
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Care_Bears

Bluey .. ... ...Teams :- Care Bears UK
Jul 7, 2007
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If you run say just 100 yards from your house or any distance , and timed yourself going and coming back at the speeds you gave, I would say you averaged at 11 mph dead, I don`t think any points are involved.
 

M600

Sock Hats are Cool!
Jan 4, 2008
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I get it to 10.9 mph.

Lets chuck some numbers in. Say I run 10 miles out, at 10mph. Thats 10 mile in 60 mins, 6 min miles
Then back at 12mph. So 10 mile at 12mph gives 5 min miles. So 50 mins.
60mins + 50 mins =110mins
Ran 20 miles in 110 mins
S = d/t = 20/110 = 0.1818 miles per min
x 60 = 10.9mph
Yep, since you were running slower for longer your average speed will be less than 11mph

Nice little brain bender