A boat can travel 48 km upstream in 6 hours. If the speed of the stream is 2 km/hr, how much time will the boat take to cover a distance of 120 km downstream?
A
20 hours
B
18 hours
C
10 hours
D
19 hours
উত্তরের বিবরণ
Question: A boat can travel 48 km upstream in 6 hours. If the speed of the stream is 2 km/hr, how much time will the boat take to cover a distance of 120 km downstream?
Solution:
Distance covered by a boat in 6 hours = 48 km
Rate upstream of boat = 48/6
= 8 km/hr
Now,
Speed of stream = 2 km/hr
∴ Speed of boat in still water = (8 + 2)
= 10 km/hr
∴ Rate downstream of boat = (10 + 2) km/hr
= 12 km/hr
∴ Time taken in covering 120 km distance = 120/12
= 10 hours
0
Updated: 6 hours ago
A train passes a man at 110 kmph running towards the train at the speed of 10 kmph. If it took 3 seconds to cross the man, what would be the length of the train?
Created: 6 hours ago
A
300 m
B
100 m
C
250 m
D
180 m
Question: A train passes a man at 110 kmph running towards the train at the speed of 10 kmph. If it took 3 seconds to cross the man, what would be the length of the train?
Solution:
As both of them are facing towards each other.
total speed will be = 110 + 10 kmph
= 120 kmph
length of the train = 120 × (3/3600) km
= 0.1 km
= 100 m
0
Updated: 6 hours ago
A train 250 meters long is running at a speed of 90 km/h. How long will it take to cross a platform 150 meters long?
Created: 6 hours ago
A
24 seconds
B
28 seconds
C
16 seconds
D
30 seconds
Question: A train 250 meters long is running at a speed of 90 km/h. How long will it take to cross a platform 150 meters long?
Solution:
speed = 90 km/h = 90 × (5/18) m/s
= 25 m/s
To cross the platform have to travel = (250 + 150) m
= 400 m
∴ Required time = 400/25 seconds
= 16 seconds
0
Updated: 6 hours ago
A man can row upstream at 10 kmph and downstream at 20 kmph. Find the man's rate in still water and the rate of the stream.
Created: 6 hours ago
A
12 kmph , 7 kmph
B
15 kmph , 5 kmph
C
15 kmph , 12 kmph
D
10 kmph , 5 kmph
Question: A man can row upstream at 10 kmph and downstream at 20 kmph. Find the man's rate in still water and the rate of the stream.
Solution:
If a is rate downstream and b is rate upstream
Rate in still water = (a + b)/2
Rate of current = (a - b)/2
Rate in still water = (20 + 10)/2 = 15 kmph
Rate of current = (20 - 10)/2 = 5 kmph
0
Updated: 6 hours ago
