Question
Speed of a boat in still water is 18 km/h while the
speed of stream is ____ km/h. Total time taken by the boat to go 90 km upstream and 210 km downstream is ____ hours. The values given in which of the following options will fill the blanks in the same order in which it is given to make the above statement true: I. 7, 20 II. 5, 15 III. 9, 22.5 IV. 3, 16Solution
For I: Speed of boat = 18 km/h Speed of stream = 7 km/h Speed in upstream = 18 – 7 = 11 km/h Speed in downstream = 18 + 7 = 25 km/h Total time = 90/11 + 210/25 = 8.18 + 8.4 = 16.58 hours So, I can’t be the answer. For II: Speed of boat = 18 km/h Speed of stream = 5 km/h Speed in upstream = 18 – 5 = 13 km/h Speed in downstream = 18 + 5 = 23 km/h Total time = 90/13 + 210/23 = 6.92 + 9.13 = 16.05 hours So, II can’t be the answer. For III: Speed of boat = 18 km/h Speed of stream = 9 km/h Speed in upstream = 18 – 9 = 9 km/h Speed in downstream = 18 + 9 = 27 km/h Total time = 90/9 + 210/27 = 10 + 7.78 = 17.78 hours So, III can’t be the answer. For IV:
x =3 → 90/15 + 210/21 = 6 + 10 = 16 So, IV can be the answer.
Train X, traveling at a speed of 54 km/hr, crosses another train Y, which is moving in the opposite direction at a speed of 90 km/hr, in 't' seconds. If...
A train is running with the speed of 72 kmph crosses a pole in 25 sec. In how much time it can cross a 160 m long platform?
A train of length 300 metres crosses a man standing on platform in 15 seconds. If its speed decreases by 20%, then find the time taken by train to cros...
Train P starts from Lucknow to Dehradun at 11:55 am with an average speed of 30 m/s. Train Q starts from Dehradun to Lucknow at 1:35 pm with an average ...
- Train P is 180 m long and crosses a platform of 120 m in 15 seconds. The speed ratio of train P to train Q is 4:5. What is the length of train Q if it cros...
A train crosses a bridge in 15 secs while it crosses a man standing on a platform in 8 secs. If the speed of train 108 km/hrs, then what will be the ti...
Length of a train is double the length of a platform. If the train crosses the platform in 72 seconds, then find the time taken by train to cross a pole.
When a train covered a distance of 1235km in 19 hours. Then the average speed of a car is 4 /5 the average speed of the train. Then, what will be the di...
Two trains of same length are running in parallel tracks in the same direction with speed 50 km/hr and 110 km/hr respectively. The latter completely cro...
A train can cross a pole and a platform of 300 meters long in 8 sec and 20 sec respectively. Find the time taken by the train to cross another platform ...
Relevant for Exams:
