In a journey of three unequal laps, a car covers a distance of 200 km in 4 h in the firs lap, while another 162 km at the speed of 15 m/s in the second lap. It covered the remaining distance of the final lap in 4 h such that the average speed of the car for entire journey was 50 km/h. What was the speed of the car in the third lap of the journey?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 47 km/h
As we know that
Average speed = Total distance/ Total time
Speed = Distance/Time
Given that
First lap distance = 200 km covered in 4 hour
Second lap distance = 162 km covered with speed of 15 m/s or 54km/h
The Average speed of car for entire journey = 50 km/h
Let remaining distance is D which is covered in 4 hour
Calculation
50 = (200 + 162 + D)/(4 + (162/54) + 4)
50 = (362 + D)/11
D = 550 - 362
D = 188 km
Hence, the speed of the third lap = 188/4 = 47km/h