SOLUTION: One third of a certain journey was covered at the speed of 25 km per hour. One forth at the rate of 30 km per hour and the rest at the rate of 50 km per hour. find the average per

Question 473576: One third of a certain journey was covered at the speed of 25 km per hour. One forth at the rate of 30 km per hour and the rest at the rate of 50 km per hour. find the average per hour of the whole journey?
Options-
1. 33 1/3 km/hr
2. 25 km/hr
3. 60 km/hr
4. 65 km/hr
5. none.
please answer it and explain it.
Thanks.
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
One third of a certain journey was covered at the speed of 25 km per hour. One forth at the rate of 30 km per hour and the rest at the rate of 50 km per hour. find the average per hour of the whole journey?
--------------------
d = total distance
t = total time
d/3 at 25
d/4 at 30
5d/12 at 50
-----------
t = (d/3)/25 + (d/4)/30 + (5d/12)/50
150t = 2d + 5d/4 + 5d/4 = 9d/2
300t = 9d
t = 3d/100
d = 100t/3
d/t = rate = 100/3
= 33 1/3 km/hr
-------------------
Options-
1. 33 1/3 km/hr

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