A person travels three equal distance at a speed of x km/hr, y km/hr and z km/hr respectively. What is the average speed for the whole journey ?
A. $$\frac{{xyz}}{{3\left( {xy + yz + zx} \right)}}$$ km/hr
B. $$\frac{{xyz}}{{\left( {xy + yz + zx} \right)}}$$ km/hr
C. $$\frac{{\left( {xy + yz + zx} \right)}}{{xyz}}$$ km/hr
D. $$\frac{{3xyz}}{{\left( {xy + yz + zx} \right)}}$$ km/hr
Answer: Option D
Solution(By Examveda Team)
Let each distance be equal to dThen, total distance travelled = 3d
Total time taken :
$$\eqalign{ & = \left( {\frac{d}{x} + \frac{d}{y} + \frac{d}{z}} \right){\text{hr}} \cr & = \frac{{d\left( {xy + yz + zx} \right)}}{{xyz}}{\text{ hr}} \cr} $$
∴ Average speed :
$$\eqalign{ & = \left[ {3d \times \frac{{xyz}}{{d\left( {xy + yz + zx} \right)}}} \right]{\text{km/hr}} \cr & = \frac{{3xyz}}{{\left( {xy + yz + zx} \right)}}{\text{ km/hr}} \cr} $$
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