A man completed a certain journey by a car. If he covered 30% of the distance at the speed of 20 km/hr, 60% of the distance at 40 km/hr and the remaining distance at 10 km/hr, his average speed for the whole journey was :
A. 25 km/hr
B. 28 km/hr
C. 30 km/hr
D. 33 km/hr
Answer: Option A
Solution(By Examveda Team)
Let 10% of journey's = 40 kmThen, total journey = 400 kms
And, $${\text{Average speed }} = \frac{{{\text{Total distance }}}}{{{\text{Total time}}}}$$
$$\eqalign{ & 30\% {\text{ of journey}} = 400 \times \frac{{30}}{{100}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 120{\text{ km}} \cr & 60\% {\text{ of journey}} = 400 \times \frac{{60}}{{100}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 240{\text{ km}} \cr & 10\% {\text{ of journey}} = 400 \times \frac{{10}}{{100}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 40{\text{ km}} \cr & {\text{Average speed}} = \frac{{400}}{{\frac{{120}}{{20}} + \frac{{240}}{{40}} + \frac{{40}}{{10}}}} \cr & {\text{Average speed}} = \frac{{400}}{{\left( {6 + 6 + 4} \right)}} \cr & {\text{Average speed}} = \frac{{400}}{{16}} \cr & {\text{Average speed}} = 25{\text{ km/hr}} \cr} $$
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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