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:
विकल्प
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
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:
Two trains, one from Howrah to Patna and other from Patna to Howrah start simultaneously. After they meet, the trains reach their destinations after 9 hours and 16 hours respectively. The ratio of their speed is.
Choose the most appropriate option:
A train which is moving at an average speed of 40 kmph, reaches its destination on time. When its average speed reduces to 35 kmph, then it reaches its destination 15 minutes late. The distance travelled by train 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?
120 men had food provision for 200 days. After 5 days, 30 men died of an epidemic. The food will last for further
Ram is traveling by car at a rate of 40 kmph. After 80 km he rests for 20 minutes. How long will he take to cover a distance of 240 kms?
There is a leak in the bottom of a tank. This leak can empty a full tank in 8 hours. When the tank is full, a tap is opened into the tank which admits 6 litres per hour and the tank is now emptied in 12 hours. What is the capacity of the tank?
Two trains, each 100 m long, moving in opposite directions, cross each other in 8 s. If one is moving twice as fast the other, then the speed of the faster train is
The ratio of length of two trains is 5 : 3 and the ratio of their speed is 6 : 5. The ratio of time taken by them to cross a pole is
The ratio of speed of the boat to that of the current is 7 : 3. If the boat goes downstream in 6 hrs 20 minutes, then it will return in
