Find the average speed of a boy if he walks 1/3rd distance with a speed of 2 m/sec and rides a bike to cover the remaining distance with a speed of 12 m/s. The total distance is 1.44 km.
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A.
18.4 km/hr
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B.
20.5 km/hr
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C.
15.8 m/hr
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D.
16.2 km/hr
Correct Answer:
D. 16.2 km/hr
Explanation:
To calculate the average speed for the boy's entire journey, we must first determine the time taken for each segment of the trip. The total distance is 1.44 km, which is equal to 1,440 meters.1. First Segment (Walking):
The boy walks 1/3rd of the total distance.
Distance = 1,440 m / 3 = 480 m
Speed = 2 m/s
Time = Distance / Speed = 480 / 2 = 240 seconds
2. Second Segment (Biking):
The remaining distance is 2/3rds of the total.
Distance = 1,440 m - 480 m = 960 m
Speed = 12 m/s
Time = Distance / Speed = 960 / 12 = 80 seconds
3. Total Calculation:
Total Distance = 1,440 m (or 1.44 km)
Total Time = 240 + 80 = 320 secondsTo find the average speed in km/hr, we convert the total time into hours:
320 seconds / 3,600 seconds/hr = 0.0888 hours
Average Speed = Total Distance / Total Time
Average Speed = 1.44 km / 0.0888 hours = 16.2 km/hr
Therefore, the correct option is d.
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