Topics

General Knowledge
General Science
General English
Aptitude
General Computer Science
General Intellingence and Reasoning
Current Affairs
Exams
Elementary Mathematics
English Literature

The respective ratio between speed of the boat upstream and speed of the boat downstream is 3 : 4. What is the speed of the boat in still water if it covers 70 km downstream in 3 hours 30 minutes? (in km/h)

A) 18
B) 18.5
C) 17
D) 17.5

Correct Answer:




D) 17.5

Description for Correct answer:
Rate downstream

= 4x kmph

Rate upstream = 3x kmph

According to the question.

\( \Large Time = \frac{\ Distance}{\ Speed} \)

\( \Large \frac{70}{4x} = 3 \frac{1}{2} \)

=> \( \Large \frac{70}{4x} = \frac{7}{2} \)

=> \( \Large \frac{10}{2x} = 1 \)

=> 2x = 10 => x = 5

\( \Large \therefore Rate \ upstream = 5 \times 3 = 15 kmph \)

\( \Large \ Rate \ downstream = 5 \times 4 = 20 kmph \)

\( \Large \therefore \ Speed \ of \ boat \ in \ still \ water \)

= \( \Large \frac{1}{2} (20 + 15 ) \ kmph \)

= \( \Large \frac{35}{2} = 17.5 \ kmph \)s

Part of solved Aptitude questions and answers : >> Aptitude

Comments

Similar Questions

1). A tank has two inlets : A and B. A alone takes 2 hours and B alone takes 3 hours to fill the empty tank completely when there is no leakage. A leakage was caused which would empty the full tank completely in 'x' hours when no inlet is open. Now, when only inlet A was opened, it took 3 hours to fill the empty tank completely. How much time will B alone take to fill the empty tank completely ? (in hours)

A). 4.5

B). 7.5

C). 3

D). 6

2). Time taken by a boat in going upstream a certain distance is twice the time taken in going the same distance downstream. Find the speed of boat upstream if it covers 20 km downstream in 1 hour 40 minutes.

A). 6 kmph

B). 7 kmph

C). 6.5 kmph

D). 7.2 kmph

3). The time taken by a boat to travel a distance downstream is half the time taken by it to travel the same distance upstream. What is the speed of the boat downstream if it travels 7.5 km upstream in 1 hour 30 minutes ? (in km/h)

A). 7.5

B). 5

C). 9

D). 10

4). Pipe A and B can fill a tank in 10 hours and 8 hours respectively. After certain time, pipe A was closed. It took a total of 6 hours to fill the tank completely. For how many hours did pipe A work?

A). \( \Large 4 \frac{1}{4} \ hours \)

B). \( \Large 2 \frac{1}{2} \ hours \)

C). \( \Large 3 \frac{1}{3} \ hours \)

D). \( \Large 5 \frac{1}{3} \ hours \)

5). A man takes 2.2 times as long to row a distance upstream as to row the same distance downstream. If he can row 55 km downstream in 2 hours 30 minutes. what is the speed of the boat in still water ? (in km/ h)

A). 40

B). 8

C). 16

D). 24

6). The respective ratio between speed of the boat upstream and speed of the boat downstream is 3 : 4. What is the speed of the boat in still water if it covers 70 km downstream in 3 hours 30 minutes? (in km/ h)

A). 18

B). 18.5

C). 17

D). 17.5

7). A tank has two inlets : A and B. A alone takes 2 hours and B alone takes 3 hours to fill the empty tank completely when there is no leakage. A leakage was caused which would empty the full tank completely in 'x' hours when no inlet is open. Now, when only inlet A was opened, it took 3 hours to fill the empty tank completely. How much time will B alone take to fill the empty tank completely ? (in hours)

A). 4.5

B). 7.5

C). 3

D). 6

8). The speed of a boat in still water is 15 kmph and the speed of the current is 3 kmph. The distance travelled by the boat from point A to point B downstream is 24 km more than the distance covered by the same boat from point B to point C upstream in the same time. How much time will the boat take to travel from point C to point B downstream ?

A). 2 hrs

B). 2 hrs 30 mins

C). 2 hrs 40 mins

D). 2 hrs 10 mins

9). If 2x + y = 15 , 2y + z = 25 and 2z + x = 26, what is the value of z ?

A). 4

B). 7

C). 9

D). None of these

10). The top of a 15 metre high tower makes an angle of elevation of \( \Large 60 ^{\circ} \) with the bottom of an electric pole and an angle of elevation of \( \Large 30 ^{\circ} \) with the top of the pole. What is the height of the electric pole ?

A). 5 metres

B). 8 metres

C). 10 metres

D). 12 metres