Advertisements
Advertisements
प्रश्न
Choose the most appropriate option
A man rows to a place 45 k.ms distant and back in 12 hours. He realises that he can row 5 k.ms downstream at the same time as 3 k.ms against the stream. The velocity of the stream is:
पर्याय
4 k.ms/hr
1.5 k.ms/hr
1 k.m/hr
2 k.ms/hr
Advertisements
उत्तर
2 k.ms/hr
Explanation:
Suppose that he moves 5 km downstream in x hours
Then, Speed downstream`="distance"/"Time"`
`=5/"x"` km/hr
Here, he can row 5 km with the stream at the same time as 3 km against the stream
i.e. Speed upstream`=3/5` of speed downstream
Speed upstream`=3/"x"` km/hr
He rows to a place 45 km distant and comes back in 12 hours.
`⇒41/((5/"x"))45/((3/"x"))=12`
⇒ 9x + 15x = 12
⇒ 3x + 5x = 4
⇒ 8x = 6
∴`"x"=4//8=1//2`
Hence. Speed downstream `5/"x"=5/((1/2))` = 10 km / hr
Speed upstream`=3/"x"=3/((1/2))` = 6 km/hr
∴ Ratio of stream`=1/2(10-6)`
`=1/2xx4`= 2 km/hr
APPEARS IN
संबंधित प्रश्न
A man walks from his house to the Railway station to catch a train, which is running as per schedule. If he walks at 6 km/hr, he misses the train by 9 minutes. However, if he walks at 7 km/hr, he reaches the station 6 minutes before the departure of rain. The distance of his home to the Railway Station is:
A flag pole 18 m high casts a shadow 9.6 m long. What is the distance of the top of the pole from the far end of the shadow?
Ranjeetha walks around the circular park in 15 minutes. If she walks at the rate of 5 km/hr, how much distance would she have to travel, at the minimum, to reach the centre of the park from any point on its perimeter?
A train 600 meters long is running at a speed of 90 kms/hr. If it crosses a tunnel in one minute, then the length of the tunnel is:
In a 100 meters race, A beats B by 20 meters B beats C by 5 meters. In the same race, A beats C by:
Choose the most appropriate option.
A boat travels upstream from A to B and back from B to A in 5 hours. The speed of the boat in still water is 8 km/hour and the speed of the current is 4 km/hour. Then, the distance from A to B is:
If a person travels at a speed of 40 km/h he will reach his destination on time. He covered half the journey in `2/3` of the time. At what speed (in km/h) should he travel to cover the remaining journey to reach the destination on time?
Two taps ‘A’ and ‘B’ can fill a water reservoir in 8 and 6 hours respectively. A third tap ‘C’ can empty the tank completely in 24 hours. How long would it take to fill the empty tank when all the taps are open?
In a flight of 600 km, an aircraft was slowed down due to bad weather. Its average speed for the trip was reduced by 200 km/h and the time of flight increased by 30 min. The duration of the flight is
Two trains of equal length are running on parallel lines in the same direction at 46 km/h and 36 km/h. The faster train passes the slower train in 36 s. The length of each train is
