Question : In a journey of three unequal laps, a car covers a distance of 200 km in 4 hr in the first 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 hr such that the average speed of the car for the entire journey was 50 km/hr. What was the speed of the car on the third lap of the journey?
Option 1: 47 km/hr
Option 2: 52 km/hr
Option 3: 42 km/hr
Option 4: 45 km/hr
Correct Answer: 47 km/hr
Solution : The concept used here is that the average speed is the total distance travelled divided by the total time taken. Speed in the second lap = 15 m/s = $\frac{15×18}{5}$ km/hr = 54 km/hr Time taken in second lap = $\frac{162}{54}$ hrs = 3 hrs The total time taken = 4 + 3 + 4 = 11 hrs Total distance = Average speed × Total time = 50 × 11 = 550 km So, the distance covered in the third lap = 550 - 200 - 162 = 188 km The speed in the third lap = $\frac{188}{4}$ = 47 km/hr Hence, the correct answer is 47 km/hr.
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Question : A man covers a certain distance by bike. If he covers 25% of the distance at the speed of 25 km/hr, 50% of the distance at the speed of 50 km/hr and the remaining distance at the speed of 12.5 km/hr, find his average speed over the whole journey.
Option 1: 20 km/hr
Option 2: 30 km/hr
Option 3: 25 km/hr
Option 4: 35 km/hr
Question : On a journey across Kolkata, a taxi averages 50 km/hr for 50% of the distance, 40 km/hr for 40% of it and 20 km/hr for the remaining. The average speed (in km/hr) for the whole journey is:
Option 1: 42 km/hr
Option 2: 40 km/hr
Option 3: 35 km/hr
Question : A car, during its entire journey of 5 hours, travels the first 45 minutes at a certain speed, the next 75 minutes at a speed of 85 km/hr, and the last 3 hours at a speed of 70 km/hr. During its entire journey, the average speed of the car is found to be 73 km/hr. What is the speed (in km/hr) of the car during the first 45 minutes?
Option 1: 65
Option 2: 68
Option 3: 62
Option 4: 72
Question : A car travels with a speed of 21 m/sec in the first 10 minutes, 9.0 km in the next 10 minutes and 10 km in the last 10 minutes of its journey. What is the average speed of the car in km/hr during its entire journey?
Option 1: 60.0 km/hr
Option 2: 63.2 km/hr
Option 3: 62.0 km/hr
Option 4: 65.3 km/hr
Question : A car completed a journey of 400 km in $12\frac{1}{2}$ hours. The first $\frac{3}{4}$th of the journey was done at 30 km/hr. Calculate the speed for the rest of the journey.
Option 1: 45 km/hr
Option 2: 25 km/hr
Option 3: 40 km/hr
Option 4: 30 km/hr
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