Question
A man travels from A to B at a speed of 45 km/h and returns from B to A at a speed of 90 km/h. Find his average speed for the whole journey.
Solution
Let one-way distance = D km. Time from A to B = D/45 Time from B to A = D/90 Total distance = 2D Total time = D/45 + D/90 = D(1/45 + 1/90) LCM(45, 90) = 90 1/45 = 2/90 So 1/45 + 1/90 = 2/90 + 1/90 = 3/90 = 1/30 Total time = D × 1/30 = D/30 Average speed = Total distance / Total time = 2D / (D/30) = 2D × 30/D = 60 km/h Answer: 60 km/h.
More Time and distance Questions
- Three people – Rohan, Suresh, and Tarun – run at speeds in the ratio 5:4:6. If Tarun takes 18 minutes to finish a race, how long will Rohan take to complet...
- A car can finish a certain journey in 10 hours at a speed of 42 kmph. In order to cover the same distance in 7 hours, the speed of the car (km/h) must be i...
- Train A crosses Train B, which is running in the opposite direction at a speed of 60 km/h, in 18 seconds. The ratio of the lengths of Train A to Train B is...
- ‘G’ and ‘H’ started moving towards each other at the same time with a speed of 40 km/hr and 30 km/hr, respectively. If the distance covered by ‘G’ is 20 km...
- A car travels from city ‘A’ to city ‘B’ covering (1/3)rd of the total distance in 5 hours and the rest in 7 hours. If it takes 8 hours to return to city ‘A...
- A passenger train takes 3 hours less for a journey of 180 km, if its speed is increased by 2 km/hour from its usual speed. Find the usual speed of the trai...
- A person walks a certain distance in three parts. For the first 'w - 10' km, he walks at 5 km/h, for the next 'w' km at 10 km/h, and for the final 'w + 10'...
- A delivery boy travels a certain distance from his warehouse to the customer’s house. At a speed of 15 km/h, he arrives 18 minutes late. But when riding at...
- I walk a certain distance and ride back taking a total time of 37 minutes. I could walk both ways in 55 minutes. How long would it take me to ride both way...
- Average speed of ‘A’ during a 20-hour journey is 24 km/h. If he covered the first 320 km of his journey at a speed of 20 km/h, then find the speed at which...
