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.
A
12 kmph , 7 kmph
B
15 kmph , 5 kmph
C
15 kmph , 12 kmph
D
10 kmph , 5 kmph
উত্তরের বিবরণ
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
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
The ratio between the speeds of two trains is 5 : 8. If the second train runs 600 km in 5 hours, then the speed of the first train is -
Created: 6 hours ago
A
100 kmph
B
95 kmph
C
80 kmph
D
75 kmph
Question: The ratio between the speeds of two trains is 5 : 8. If the second train runs 600 km in 5 hours, then the speed of the first train is -
Solution:
Let the speed of the trains are 5x and 8x
the speed of the second train = 600/5 kmph = 120 kmph
∴ 8x = 120
x = 15
∴ speed of first train = 5x = 75 kmph
0
Updated: 6 hours ago
An aeroplane covers a certain distance at a speed of 250 kmph in 6 hours. To cover the same distance in 100 minutes, it must travel at a speed of-
Created: 6 hours ago
A
900 km/hr
B
700 km/hr
C
800 km/hr
D
950 km/hr
Question: An aeroplane covers a certain distance at a speed of 250 kmph in 6 hours. To cover the same distance in 100 minutes, it must travel at a speed of-
Solution:
Total Distance = (250 × 6) = 1500 km.
Time 100 minutes = 100/60 hr
= 5/3 hr
We know that,
Speed = Distance/Time
∴ Required speed = 1500/(5/3) km/hr
= 900 km/hr.
0
Updated: 6 hours ago
