Speed, Time and Distance
- A train 200 m long running at 36 kmph takes 55 seconds to cross a bridge. The length of the bridge is
-
View Hint View Answer Discuss in Forum
Speed of train = 36kmph
= 36 × 5 = 10 m/sec. 18
If the length of bridge be x metre, then10 = 200 + x 55
⇒ 200 + x = 550
⇒ x = 550 – 200 = 350 metre.
Second Method :
Here, x = 200 mu = 36 km/hr, 36 × 5 m/second = 10 m/sec 18
y = ?, t = 55 sec
usingt = x + y u 55 = 200 + y 10
y = 550 – 200
y = 350 mCorrect Option: C
Speed of train = 36kmph
= 36 × 5 = 10 m/sec. 18
If the length of bridge be x metre, then10 = 200 + x 55
⇒ 200 + x = 550
⇒ x = 550 – 200 = 350 metre.
Second Method :
Here, x = 200 mu = 36 km/hr, 36 × 5 m/second = 10 m/sec 18
y = ?, t = 55 sec
usingt = x + y u 55 = 200 + y 10
y = 550 – 200
y = 350 m
- A man covers a total distance of 100 km on bicycle. For the first 2 hours, the speed was 20 km/hr and for the rest of the journey, it came down to 10 km/hr. The average speed will be
-
View Hint View Answer Discuss in Forum
Distance covered in first 2 hours
= 2 × 20 = 40 km.
Remaining distance
= 100 – 40 = 60 km.
Time taken in covering 60 km at 10 kmph= 60 = 6 hours 10 ∴ Required average speed = Total distance Total Time = 
100 
kmph 2 + 6 = 100 kmph 8 = 25 kmph 2 = 12 1 kmph 2 Correct Option: A
Distance covered in first 2 hours
= 2 × 20 = 40 km.
Remaining distance
= 100 – 40 = 60 km.
Time taken in covering 60 km at 10 kmph= 60 = 6 hours 10 ∴ Required average speed = Total distance Total Time = 100 kmph 2 + 6 = 100 kmph 8 = 25 kmph 2 = 12 1 kmph 2
- On a journey across Kolkata, a taxi averages 50 km per hour for 50% of the distance, 40 km per hour for 40% of it and 20 km per hour for the remaining. The average speed (in km/hour) for the whole journey is :
-
View Hint View Answer Discuss in Forum
Total distance = 100 km.
Total time = 50 + 40 + 10 50 40 20 = 1 + 1 + 1 = 5 hours 2 2 ∴ Average speed = 100 × 2 = 40 kmph 5 Correct Option: B
Total distance = 100 km.
Total time = 50 + 40 + 10 50 40 20 = 1 + 1 + 1 = 5 hours 2 2 ∴ Average speed = 100 × 2 = 40 kmph 5
- A train goes from Ballygunge to Sealdah at an average speed of 20 km/hour and comes back at an average speed of 30 km/hour. The average speed of the train for the whole journey is
-
View Hint View Answer Discuss in Forum
Required average speed = 2 × 30 × 20 30 + 20
[∵ Distance covered is same]= 2 × 30 × 20 = 24 kmph 50 Correct Option: D
Required average speed = 2 × 30 × 20 30 + 20
[∵ Distance covered is same]= 2 × 30 × 20 = 24 kmph 50
- A and B are 20 km apart. A can walk at an average speed of 4 km/hour and B at 6 km/hr. If they start walking towards each other at 7 a.m., when they will meet ?
-
View Hint View Answer Discuss in Forum
If A and B meet after t hours, then
4 t + 6 t = 20
⇒ 10 t = 20⇒ t = 20 = 2 hours. 10
Hence, both will meet at 9 a.m.Correct Option: C
If A and B meet after t hours, then
4 t + 6 t = 20
⇒ 10 t = 20⇒ t = 20 = 2 hours. 10
Hence, both will meet at 9 a.m.
