Converting minutes and speed to km/hr.

Jan 2013
5
0
West Coast
Been stuck on this problem and unsure how to complete.

A horse galloped a mile in 2 min 35 s. What was its average speed in km/h?

Any thoughts?
 
Jul 2012
863
232
INDIA
Horse gallops 1 mile in 2 min and 35 sec
We are to find speed in km/h
Let us first convert 2 min and 35 sec in hours
2 min and 35 sec = 2 min + 35/60 min = 2 min + 7/12 min = 31/12 min = 31/(12x 60) hours
Now the horse covers in 2 min 35 sec distance = 1 mile
i.e., the horse covers in 31/(12x 60) hours distance = 1 mile
Or the horse covers in 1 hours distance = 1 x [ (12x60)/31] mile
But 1 mile = 1.61 km
Thus the horse gallops [ 12x60/31 ] 1.61 km in 1 hour
That is the speed in km / h
 

Prove It

MHF Helper
Aug 2008
12,897
5,001
For starters, 1 mile = 1.609344 kilometres. So set up a ratio of miles : seconds, we have

1 mile : 155 sec
1.609344 km : 155 sec
1.609344 / 155 km : 1 sec
(1.609344 / 155) * 3600 km : 3600 sec
37.37831 km : 1 hr

So it's about 37 km/h.