Question

One third of a certain journey is covered at the rate of 25 km/hr. One fourth at the rate of 30 km/hr and the rest at 50 km/hr. What is the average speed of the whole journey

Answer 1

Hlo mate,

your answer is here,


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
-------------------
. 33 1/3 km/hr

I hope it helps you,....

Answer 2

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