A man can row upstream at 16 km/hr and downstream at 24 km/hr. Find the speed of the current.

Correct Answer: 3 kms

Explanation:

Let the place be at a distance of 'd' kms

From the given data,

$$\begin{gathered} d 5 - 1 + d 5 + 1 = 75 60 kms \\ d 4 + d 6 = 5 4 \\ \end{gathered}$$

5d/12 = 5/4 => d = 3 kms.

 

Hence, the place is 3 kms far.

Correct Answer: 72 km

Explanation:

Rate of her upstream = 12/2.5 = 4.8 km/hr

Then, ATQ

Rate of downstream = 4.8 x 3 = 14.4 km/hr

 

Hence, the distance she covers downstream in 5 hrs = 14.4 x 5 = 72 kms.

Correct Answer: 900 kms

Explanation:

Let the distance he covered each way = d kms

According to the question,

d/45 - d/50 = 1

=> d = 450 kms.

 

Hence, the total distance he covered in his way = d + d = 2 d = 2 x 450 = 900 kms.

Correct Answer: 8:3

Correct Answer: 3 hrs 30 min

Explanation:

Let the speed of boat and stream be x and y kmph respectively.

According to question

d/x+y + d/x-y = 5h 15m or 21/4 hrs ......(i)

and 2d/x-y = 7...... (ii)

From eq. (i) and (ii)

2d/x+y = 7/2

Hence, Amith will take to row 2d km distance downstream in 7/2 hrs

= 3.5 hrs

= 3 hrs 30 min.

Correct Answer: 1 : 3

Explanation:

Let the speed of the boat in still water is 'w'

Speed of the current is 'c'

Let the distance between two places is 'd'

According to the question, motorboat takes half time to cover a certain distance downstream than upstream.

d w + c = 1 2 d w - c

=> 2w - 2c = w + c

=> w = 3c

=> c : w = 1 : 3

 

Hence, the ratio between rate of current(c) and rate of boat in still water(w) = 1 : 3

Correct Answer: 4 kmph

Explanation:

Let the speed of current = 'C' km/hr

 

Given the speed of boat in still water = 6 kmph

 

Let 'd' kms be the distance it covers.

 

According to the given data,

 

Boat takes thrice as much time in going the same distance against the current than going with the current

 

i.e,  d 8 - C = 3 × d 8 + C

 

$$\begin{gathered} ? 24 - 3 C = 8 + C \\ ? 4 C = 16 \\ ? C = 4 kmph \end{gathered}$$

 

Hence, the speed of the current C = 4 kmph.

Correct Answer: 9 kmph

Explanation:

Speed of boat in still water = 1/2 (12 + 6) = 9 kmph.

Correct Answer: 13 kmph

Explanation:

Given that, upstream distance = 7 kms

Upstream speed = 7/42 x 60 = 10 kms

Speed of the stream = 3 kmph

Let speed in still water = M kmph, then

Upstream speed = M - 3 = 10

=> M = 13 kmph.

Correct Answer: 9