A car travels the first one-third of a certain distance with a speed of 10 km/hr, the next one-third distance with a speed of 20 km/hr, and the last one-third distance with a speed of 60 km/hr. The average speed of the car for the whole journey is :
A. 18 km/hr
B. 24 km/hr
C. 30 km/hr
D. 36 km/hr
Answer: Option A
Solution(By Examveda Team)
Let the whole distance travelled be x km and the average speed of the car for the whole journey be y km/hrThen,
$$\eqalign{ & \Leftrightarrow \frac{{\left( {\frac{x}{3}} \right)}}{{10}} + \frac{{\left( {\frac{x}{3}} \right)}}{{20}} + \frac{{\left( {\frac{x}{3}} \right)}}{{60}} = \frac{x}{y} \cr & \Leftrightarrow \frac{x}{{30}} + \frac{x}{{60}} + \frac{x}{{180}} = \frac{x}{y} \cr & \Leftrightarrow \frac{1}{{18}}y = 1 \cr & \Leftrightarrow y = 18{\text{ km/hr}} \cr} $$
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
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