One third of a certain journey is covered at the speed of 80 km/hr one fourth of the journey at the speed of 50 km/hr and the rest at the speed of 100 km/hr what will be the average speed (in km/hr) for the whole journey?
A. 75
B. 67
C. 66.66
D. 76.66
Answer: Option A
Solution(By Examveda Team)
$$\eqalign{ & {\text{Average speed}} = \frac{{{\text{Total Journey}}}}{{{\text{Time Taken}}}} \cr & \Rightarrow {\text{Remaining distance}} \cr & = 1 - \left( {\frac{1}{3} + \frac{1}{4}} \right) = \frac{5}{{12}}{\text{ km}} \cr & \therefore {\text{Average speed}} \cr & = \frac{1}{{\frac{1}{{3 \times 80}} + \frac{1}{{50 \times 4}} + \frac{{1 \times 5}}{{100 \times 12}}}} \cr & = \frac{1}{{\frac{{5 + 6 + 5}}{{1200}}}} \cr & = \frac{{1200}}{{16}} \cr & = 75{\text{ km/hr}}{\text{.}} \cr} $$Related Questions on Speed Time and Distance
A. 48 min.
B. 60 min.
C. 42 min.
D. 62 min.
E. 66 min.
A. 262.4 km
B. 260 km
C. 283.33 km
D. 275 km
E. None of these
A. 4 hours
B. 4 hours 30 min.
C. 4 hours 45 min.
D. 5 hours
Join The Discussion