a man travelled from one place to another at the rate of 20 kms/ hours and returned at the rate 30kms/hour. Find the average speed in the whole journey
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A >>>>>(20kms/hr)>>>>> B
A <<<<<(30kms/hr)<<<<< B
(Let Origin be A and destination be B)
The Average speed= (Total distance)/(Total Time)
Let's Assume distance is X kms (for one side)
so, total distance= 2X kms
Now,
T (A>B) = (X/20) hr
T (A<B) = (X/30) hr
Total time= (X/20)+(X+30)
= (3X+2X)/60
= X/12 hr
So,
Average speed= [2X/(X/12)] = 24 km/hr
You can calculate by assuming any value of X, Average speed would be same for any value. To avoid fractions, assume values by LCM of 20 and 30 (which is 60).
Hope this helps :)
A <<<<<(30kms/hr)<<<<< B
(Let Origin be A and destination be B)
The Average speed= (Total distance)/(Total Time)
Let's Assume distance is X kms (for one side)
so, total distance= 2X kms
Now,
T (A>B) = (X/20) hr
T (A<B) = (X/30) hr
Total time= (X/20)+(X+30)
= (3X+2X)/60
= X/12 hr
So,
Average speed= [2X/(X/12)] = 24 km/hr
You can calculate by assuming any value of X, Average speed would be same for any value. To avoid fractions, assume values by LCM of 20 and 30 (which is 60).
Hope this helps :)
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