- In water the direction along the stream is called downstream.
- The direction against the stream is called upstream
- Still water: It implies that the speed of the water in the river is zero.
- Stream water: It implies that the water of the river is moving.
Results
#1. A man rows upstream 20 Km and downstream 30 Km taking 5 hours each . Find the speed of current
A man rows upstream 20 Km and downstream 30 Km taking 5 hours each . Find the speed of current ?
speed of current y = 1/2 (d/t downstream -d/t upstream )
= 1/2 (30/5 – 20/5 )
1 Km/h
#2. A man can row 6 Km/h in the still water a if the river is running at 2 Km/h , it takes him 3 hours to row to a place and back . How far is the place ?
A man can row 6 Km/h in the still water a if the river is running at 2 Km/h , it takes him 3 hours to row to a place and back . How far is the place ?
=using formula = t plus t = total time
d/x plus y plus d/x-y =total time
d/8 plus d/4 = 3
d = 8 Km
#3. The speed of a boat is still water is 15 Km/h and the rate of current is 13 Km/h. Find the distance travelled downstream in 15 min ?
The speed of a boat is still water is 15 Km/h and the rate of current is 13 Km/h. Find the distance travelled downstream in 15 min ?
distance in downstream =downstream rate * time
( 15 plus 13 ) *15/60
= 7 Km
#4. A man can row at a speed of 4.5 Km/h in still water to a certain upstream point and back to the starting point in a river which flows at 1.5 Km/h . Find his average speed for total journey ?
A man can row at a speed of 4.5 Km/h in still water to a certain upstream point and back to the starting point in a river which flows at 1.5 Km/h . Find his average speed for total journey ?
X = 4.5 Km/h
Y = 1.5 Km/h
using the formula (6)
average speed for total journey
= upstream rate * downstream rate /speed in still in water
(x plus y ) * (x – y ) / x
=6*3 / 4.5
=4 Km/h
#5. In one hour , a boat goes 11 Km along the stream and 5 Km against the stream . The speed of the boat in still water is :
In one hour , a boat goes 11 Km along the stream and 5 Km against the stream . The speed of the boat in still water is :
speed in still water = 1/2 (11 plus 5 ) Kmph
= 8 Kmph
#6. A man can row three-quarters of a kilometre against the stream in 11 1/4 minutes . The speed of the man in still water is :
A man can row three-quarters of a kilometre against the stream in 11 1/4 minutes . The speed of the man in still water is :
Rate upstream = ( 750 / 675 )m/sec = ( 10 / 9 ) m/sec;
Rate downstream = ( 750 / 450 )m/sec =5/3 m/sec .
Rate in still water = 1/2(10/9 plus 5/3 ) m/sec
= 25/18 m/sec
= ( 35/18 *18/5 ) Km/hr
= 5 Km/hr
#7. A man sped with the current is 15 Km /hr and the speed of the current is 2.5 Km/hr. The man speed against the current is :
A man sped with the current is 15 Km /hr and the speed of the current is 2.5 Km/hr. The man speed against the current is :
Man’s rate in still water = (15 – 2.5 ) Km/hr
=12.5 Km/hr
Man’s rate against the current = ( 12.5 – 2.5 ) Km/hr
=10 km/hr
#8. If a man rows at the rate of 5 Kmph in still water and his rate against the current is 3.5 kmph , then the man rate along current is :
If a man rows at the rate of 5 Kmph in still water and his rate against the current is 3.5 kmph , then the man rate along current is :
Let the rate along he current be x Kmph
then , 1/2 (x plus 3.5 ) = 5
x = 6.5 Kmph
#9. The speed of the boat in still water is 15 Km/hr and the rate of current is 3 Km/hr. The distance travelled downstream in 12 minutes is :
The speed of the boat in still water is 15 Km/hr and the rate of current is 3 Km/hr. The distance travelled downstream in 12 minutes is :
speed downstream = ( 15 plus 3 ) Kmph =18 Kmph
distance travelled = ( 18 * 12 /60 ) Km
= 3.6 Km
#10. A motor boat whose speed is 15 km/hr in still water goes 30 km downstream and comes back in a total of a 4 hours 30 minutes, The speed of the stream is :
A motor boat whose speed is 15 km/hr in still water goes 30 km downstream and comes back in a total of a 4 hours 30 minutes, The speed of the stream is :
Let the speed of stream be x kmph
Then speed of stream = (15 plus x)kmph
speed of stream = (15-x)kmph
30/(15 plus x) plus 30 /(15-x) = 4 1/2
900/ 225 – x²= 9/2
9x²=225
x²=25
x= 5 kmph
#11. The speed of a boat in still water is 10 km/hr. If it can travel 26 km down stream and 14 km upstream in the same time the speed of the stream is :
Let the speed of the stream x km/hr
Then speed downstream = (10 plus x) km/hr
Speed up stream = ( 10- x)km/hr
26/(10 plus x) = 14(10-x)
260- 26x = 140 plus 14x
40x = 120
x=3km/hr
#12. A man can row up stream at 7 km/hr and downstream at 10 km/hr Find man’s rate in still water and the rate of current
A man can row up stream at 7 km/hr and downstream at 10 km/hr Find man’s rate in still water and the rate of current
Rate in still water = 1/2 (10 plus 7 )km/hr
= 8.5 km/hr
Rate of current = 1/2 (10-7 ) km/hr
= 1.5 km/hr
#13. A man can rows at 5 kmph in still water if the velocity of current is 1 kmph at it takes him 1 hours to row to a place and come back, how far is the place?
A man can rows at 5 kmph in still water if the velocity of current is 1 kmph at it takes him 1 hours to row to a place and come back, how far is the place?
Speed downstream = (5 plus 1 ) kmph = 6 kmph
Speed upstream = ( 5-1) kmph = 4 kmph
Let distance be x km
then x/6 plus x/4 =1
2x plus 3x =12
5x = 12
x= 2.4 km
#14. A man can row upstream at 7 kmph and downstream at 10 kmph. Find man’s rate in still water and the rate of current.
A man can row upstream at 7 kmph and downstream at 10 kmph. Find man’s rate in still water and the rate of current.
Rate in still water = 1/2 ( 10 plus 7)kmph
= 8.8 km/hr
Rate of current = 1/2(10 – 7) km/hr
1.5 km/hr
#15. A man can swim in still water at 4.5 km/hr,but takes twice as long to swim upstream than downstream. The speed of the stream is
A man can swim in still water at 4.5 km/hr,but takes twice as long to swim upstream than downstream. The speed of the stream is
correct answer is 1.5
#16. A man rows 40 km upstream in 8 hours and a distance of 36 km downstream in 6 hours, then speed of stream is
A man rows 40 km upstream in 8 hours and a distance of 36 km downstream in 6 hours, then speed of stream is
Hint : Rate of stream = 1/2 (distance down stream / time down stream – distance of upstream / time cove upstream )
correct Answer= 0.5 km/ hr
#17. If a man’s downstream rate is 10 km/hr and the rate of stream is 1.5 km/h then the man upstream rate is
#18. If a man goes upstream at 6 km /hr and the rate of stream is 2 km/hr then the man speed in still water is :
If a man goes upstream at 6 km /hr and the rate of stream is 2 km/hr then the man speed in still water is :
Hint upstream rate =( speed in still water- speed of stream )
#19. A boat goes 100 km downstream in 10 hours and 75 km upstream in 15 hours. The speed of the stream is
A boat goes 100 km downstream in 10 hours and 75 km upstream in 15 hours. The speed of the stream is
correct answer= 2 1/2 km/hr
#20. A man can row his boat with the stream st 6km/hr and against the stream in 4 km/ hr. The man’s rates
A man can row his boat with the stream st 6km/hr and against the stream in 4 km/ hr. The man’s rates
Correct Answer is =5 km/hr