A boat whose speed in still water is 9 kmph, goes 12 km downstream and comes bac

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Question
A boat whose speed in still water is 9 kmph, goes 12 km downstream and comes back in 3 hrs. Find the speed of the stream?
Options
A. 1 kmph
B. 3 kmph
C. 5 kmph
D. 4 kmph

Correct Answer

3 kmph

Explanation

Let the speed of the stream = x kmph

From the given data,

$\frac{12}{9 + x} + \frac{12}{9 - x} = 3 h r s$

$3 x^{2} = 27$

=> x = 3 kmph

Therefore, the speed of the stream = 3 kmph

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1. A boat running upstream takes 8 hours 48 minutes to cover a certain distance, while it takes 4 hours to cover the same distance running downstream. What is the ratio between the speed of the boat and speed of the water current respectively?
Options
A. 7:4
B. 11:4
C. 4:7
D. 8:3

2. A man can row 6 kmph in still water. When the river is running at 1.2 kmph, it takes him 1 hour to row to a place and back. What is the total distance traveled by the man ?
Options
A. 4.58 kms
B. 6.35 kms
C. 5.76 kms
D. 5.24 kms

3. A boatman can row 3 km against the stream in 20 minutes and return in 18 minutes. Find the rate of current ?
Options
A. 1/3 kmph
B. 2/3 kmph
C. 1/4 kmph
D. 1/2 kmph

4. A man rows his boat 60 km downstream and 30 km upstream taking 3 hrs each time. Find the speed of the stream ?
Options
A. 5 kmph
B. 10 kmph
C. 15 kmph
D. 45 kmph

5. A man goes down stream with a boat to some destination and returns upstream to his original place in 5 hours. If the speed of the boat in still water and the strean are 10km/hr and 14km/hr respectively, the distance of the destination from the string place is
Options
A. 16 km
B. 18 km
C. 21 km
D. 25 km

6. A man can row 8 kmh in still water. If the river is running at 2 kmh, it takes 4 hrs more upstream than to go downstream for the same distance. Then the distance is given by
Options
A. 54 kms
B. 32 kms
C. 45 kms
D. 60 kms

7. A motorboat can go 10 miles downstream on a river in 20 min. It takes 30 min for this boat to go back at the same 10 miles. Find the speed of the current ?
Options
A. 8 m/h
B. 5 m/h
C. 7 m/h
D. 6 m/h

8. In one hour, a boat goes 12 km/hr along the stream and 6 km/hr against the stream. The speed of the boat in still water (in km/hr) is:
Options
A. 9
B. 8
C. 7
D. 7.5

9. If sum of upstream and downstream speed of a boat is 82 kmph, and the boat travels 105 km. upstream in 3 hr, Find the time taken by boat to cover 126 km downstream.
Options
A. 2.8 hrs
B. 2.7 hrs
C. 2.6 hrs
D. 2.5 hrs

10. A boat travels 72 km downstream in 8 hours and 84 km upstream in 12 hours. Find the speed of the boat in still water and the speed of the water current ?
Options
A. 9 and 3 kmph
B. 6 and 7 kmph
C. 8 and 1 kmph
D. 7 and 2 kmph

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