- A boat running downstream covers a distance of 36 km in 4 hrs and for covering the same distance upstream it takes 9 hrs. What is the speed of the stream?
2.5 km/hr3 km/hr4.5 km/hr5 km/hrNone of theseOption A
Downstream speed = 36/4 = 9 km/hr
Upstream speed = 36/9 = 4 km/hr
So, speed of stream = 1/2*(9-4)=2.5 km/hr
- It takes 5 times as long to row a distance against the stream as to row the same distance in favor of stream. What is the ratio of the speed of the boat in still water to that of stream?
7:53:22:51:6None of theseOption B
B = [t1u + t1d] / [t1u – t1d] * R
So,B =[5x + x] / [5x- x] * R
So B/R = 6/4 = 3:2
- Rakesh rows to a place 40 km distant and back in total of 18 hours. He finds that he can row 5 km with the stream in same time as 4 km against the stream. What is the speed of boat in still water?
3.0 km/hr4.5 km/hr4.5 km/hr6 km/hr5 km/hrOption C
Suppose he moves 5 km downstream in t hours
Then, downstream speed a= 5/t km/hr
Speed upstream speed b = 4/t km/hr
40 / (5 /t) + 40 / (4/t) = 18
8t + 10t = 18
t = 1
a = 5 km/hr, b = 4 km/hr
speed of boat = ½ (5 + 4 ) =4.5 km/hr
- If Neelaksh can swim downstream at 6 kmph and upstream at 2 kmph.What is his speed in still water ?
9 km/hr7 km/hr5 km/hr4 km/hrNone of theseOption D
Speed downstream a = 6 kmph
Speed upstream b = 2kmph
Speed in still water = ½ (a+b) kmph
= ½ (6+2) = 8/2 = 4kmph
- Akansha can row upstream at 8 kmph and downstream at 12 kmph.What is the speed of the stream ?
5 km/hr7 km/hr8 km/hr5 km/hr2 km/hrOption E
Speed of the stream = ½ (x-y) = ½ (12-8)
= 4/2 = 2 kmph
- Ramesh rows to a place 48 km distant and back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against stream. Find the rate of the stream?
1 km/hr3 km/hr5 km/hr6 km/hrNone of theseOption A
Speed of the stream = ½ (x-y) km/ hr
Speed = distance traveled / time taken
- Shivani can row a boat at 10 kmph in still water. If the speed of the stream is 6 kmph, the time taken to row a distance of 80 km down the stream is ?
is5 hours2 hours3 hours4 hoursNone of theseOption A
Speed in still water, ½ (a+b) = 10 km/hr
a+b = 20 km/hr…………….(1)
speed of the stream, ½ (x-y) = 6km/hr
x-y = 12 km/hr …………….(2)
(1)+(2 ) we get 2x = 32
x= 16 km/hr
speed downstream =distance traveled / time taken
time taken = 80/16 = 5 hours
- Srikant can row 9 (1/3) kmph in still water and finds that it takes him thrice as much time to row up than as to row down the same distance in the river. What is speed of current ?
4 (2/3) km/hr7 (2/3) km/hr5 (1/3) km/hr7 km/hrNone of theseOption A
Speed in still water = 9 (1/3) = 28/3 km/hr
i.e, ½ (x+y) = 28/3 km/hr
=½ (x+3x) = 28/3
2x = 28/3 = x = 28/ 2 x 3 = 14/3 km/hr
rate upstream = 14/3 km/hr and
rate downstream = 14/3 x 3 = 14 km/hr
speed of the current = ½ (x-x) = ½ (14 – 14/3)
= ½ (42-14/3) = 28/6 = 4 (2/3) km/hr
- Vikas goes downstream 60 km and upstream 20 km, taking 4 hrs each. What is the speed of current?
8 km/hr5 km/hr10 km/hr2 km/hr4 km/hrOption B
Downstream speed = 60/4 = 15 km/hr
Upstream speed = 20/4 = 5 km/hr
Speed of stream = (15-5)/2 = 5 km/hr
- Akash rows downstream 28 km and upstream 16 km, taking 5 hrs each time. What is the velocity of current?
1.2 km/hr1.8 km/hr2 km/hr1.5 km/hrNone of theseOption A