A Woman?s downstream swimming rate is thrice of her upstream swimming rate. If she covers 12 km upstream in 2.5 hours, what distance she will cover in 5 hours downstream?

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: 2.83 kmph

Explanation:

Given speed of the person = 8 1/2 = 17/2 kmph
Let the speed of the stream = x kmph
speed of upstream = 17/2 - x
speed of downstream = 17/2 + x
But given that,
2(17/2 - x) = 17/2 + x
=> 3x = 17/2
=> x = 2.83 kmph.

Correct Answer: 1.5 kmph

Explanation:

72 --- 9
? ---- 1

=> Down Stream = 8

45 ---- 9 
? ---- 1

=> Up Stream = 5

Speed od current S = ?

S = (8 - 5)/2 = 1.5 kmph.

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: 4 kmph

Explanation:

Speed of the current = 24-16/2

= 8/2

= 4 km/hr.

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.