A boat while travelling upstream covers a distance of 29 km at the speed of 6 km/h, whereas while travelling downstream it covers the same distance at a speed of 12 km/h. What is the speed of the boat in still water?

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: 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:

Speed of the current = 24-16/2

= 8/2

= 4 km/hr.

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: 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

Correct Answer: 4.5 km/h and 0.5 km/h

Explanation:

Distance travelled by boat in upstream=24km

Time taken = 6 h

Speed of the boat in upstream = 24/6 = 4 km/h

And distance travelled by boat in downstream = 20 km

Time taken = 4h Speed of the boat in downstream = 20/4 km/h = 5 km/h

Now, speed of the boat in still water = 1/2 [ speed of the boat in upstream + speed of the boat in downstream] =1/2 [4 + 5] = 1/2 × 9 = 4.5 km/h

And speed of the current = 1?2 [speed of the boat in downstream ? speed of the boat in upstream] = 1/2 [5 ? 4] = 1/2 × 1 = 0.5 km/h

Correct Answer: 9 kmph

Explanation:

Downstream speed = 8/X kmph

upstream speed = 4/X kmph

Now 80/(8/X) + 80/(4/X)=20

X=2/3

downstream Speed = 8/(2/3)= 12 kmph

upstream Speed = 4/(2/3)= 6 kmph

Rate of the stream = (12+6)/2= 9 kmph

Correct Answer: 50

Explanation:

let speed of boat= X, speed of stream= Y
Upstream speed= X-Y
Downstream speed= X+Y
Sum of upstream & downstream= (X-Y) +(X+Y)= 2X
So, 2X= 40
X= 20 km/hr
Speed of boat : speed of stream= 600+100 :100= 7:1
So speed of Stream= 20/7 km/hr
ATQ, D/( X-Y) + D/( X+Y) = 5
D/(120/7) + D/(160/7)= 5
D= 480×5/49= 48.97 km= 50 Km(approx)