37
Q:

# A boat sails 15 km of a river towards upstream in 5 hours. How long will it take to cover the same distance downstream, if the speed of current is one-fourth the speed of the boat in still water:

 A) 1.8h B) 3h C) 4h D) 5h

Explanation:

Upstream speed = B-S

Downstream speed = B+s

B-S = 15/5 = 3 km/h

Again          B= 4S

Therefore    B-S = 3= 3S

=>             S = 1 and B= 4 km/h

Therefore    B+S = 5km/h

Therefore, Time during downstream = 15/5 = 3h

Q:

Sravan drove from home to a neighboring town at the speed of 50 km/h and on his returning journey, he drove at the speed of 45 km/h and also took an hour longer to reach home. What distance did he cover?

 A) 350 kms B) 450 kms C) 900 kms D) 700 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.

1 125
Q:

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?

 A) 6 kmph B) 8 kmph C) 9 kmph D) 11 kmph

Explanation:

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

1 354
Q:

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?

 A) 72 km B) 36 km C) 56 km D) 42 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.

2 776
Q:

A man went downstream for 28 km in a motor boat and immediately returned. It took the man twice as long to make the return trip. If the speed of the river flow were twice as high, the trip downstream and back would take 672 minutes. Find the speed of the boat in still water and the speed of the river flow.

 A) 12 km/hr, 3 km/hr B) 9 km/hr, 3 km/hr C) 8 km/hr, 2 km/hr D) 9 km/hr, 6 km/hr

Explanation:

Let the speed of the boat = p kmph

Let the speed of the river flow = q kmph

From the given data,

=> 56p - 56q -28p - 28q = 0

=> 28p = 84q

=> p = 3q.

Now, given that if

Hence, the speed of the boat = p kmph = 9 kmph and the speed of the river flow = q kmph = 3 kmph.

0 1359
Q:

Rajesh rows in still water with a speed of 4.5 kmph to go to a certain place and comes back. Find his average speed for the whole journey, if the river is flowing with a speed of 1.5 kmph?

 A) 2 kmph B) 4 kmph C) 6 kmph D) 8 kmph

Explanation:

Let the distance in one direction = k kms

Speed in still water = 4.5 kmph

Speed of river = 1.5

Hence, speed in upstream = 4.5 - 1.5 = 3 kmph

Speed in downstream = 4.5 + 1.5 = 6 kmph

Time taken by Rajesh to row upwards = k/3 hrs

Time taken by Rajesh to row downwards = k/6 hrs

Now, required Average speed =

Therefore, the average speed of the whole journey = 4kmph.

1 909
Q:

A boat takes 2 hours to travel from point A to B in still water. To find out its speed upstream, which of the following information is/are required?

A. Distance between point A and B.

B. Time taken to travel downstream from B to A.

C. Speed of the stream of water.

 A) Only A and B B) Only B and C C) All are required D) Any one pair of A and B, B and C or C and A is sufficient

Answer & Explanation Answer: D) Any one pair of A and B, B and C or C and A is sufficient

Explanation:

Let distance between A & B = d km
Let speed in still water = x kmph
Let speed of current = y kmph

from the given data,
d/x = 2

From A) we get d
From B) we get d/x+y
From C) we get y

So, Any one pair of A and B, B and C or C and A is sufficient to give the answer i.e, the speed of upstream.

0 1188
Q:

A man can row against the current three fourth of a kilometer in 15 min and returns same distance in 10 min, then ratio of his speed to that of current?

 A) 5:1 B) 3:1 C) 4:1 D) 2:1

Explanation:

Let the speed of the man in still water = p kmph

Speed of the current = s kmph

Now, according to the questions

(p + s) x 10 = (p - s) x 15

2p + 2s = 3p - 3s

=> p : s = 5 : 1

Hence, ratio of his speed to that of current = 5:1.

4 880
Q:

A motorboat goes 8 km an hour in still water, but takes thrice as much time in going the same distance against the current than going with the current. Then find the speed of the current?

 A) 4 kmph B) 6 kmph C) 3 kmph D) 2 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,

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