Quantitative Aptitude

General Questions

Quantitative Aptitude Exercise Mode

General Questions

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Question 1
In one hour, a boat goes 11 km along the stream and 5 km against the stream. The speed of the boat in still water (in km/hr) is :

A
3 km/hr
B
5 km/hr
C
8 km/hr
D
9 km/hr
Correct Answer: Option C

Speed in still water = 1 (11 + 5) kmph = 8 kmph.
2

Question 2
A boat running upstream takes 8 hours 48 minutes to cover a certain distance, while it takes 4 hours to cover the same distance running downstream. What is the ratio between the speed of the boat and speed of the water current respectively ?

A
2 : 1
B
3 : 2
C
8 : 3
D
Cannot be determined
E
None of these
Correct Answer: Option C

Let the man's rate upstream be x kmph and that downstream be y kmph.

Then, distance covered upstream in 8 hrs 48 min = Distance covered downstream in 4 hrs.

x x 8 4 = (y x 4)
5

44 x =4y
5

y = 11 x.
5

Required ratio = y + x : y - x
2 2

   = 16x x 1 : 6x x 1
5 2 5 2

   = 8 : 3
5 5

   = 8 : 3.

Question 3

A man can row three-quarters of a kilometre against the stream in 11 minutes and down the stream in 7 minutes. The speed (in km/hr) of the man in still water is:

A
2
B
3
C
4
D
5
Correct Answer: Option D

We can write three-quarters of a kilometre as 750 metres,

and 11 minutes as 675 seconds.

Rate upstream = 750 m/sec = 10 m/sec.
675 9

Rate downstream = 750 m/sec = 5 m/sec.
450 3

Rate in still water = 1 10 + 5 m/sec
2 9 3

   = 25 m/sec
18

   = 25 x 18 km/hr
18 5

   = 5 km/hr.

Question 4
A man's speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr. The man's speed against the current is :

A
8.5 km/hr
B
9 km/hr
C
10 km/hr
D
12.5 km/hr
Correct Answer: Option C

Man's rate in still water = (15 - 2.5) km/hr = 12.5 km/hr.

Man's rate against the current = (12.5 - 2.5) km/hr = 10 km/hr.

Question 5
A motorboat, whose speed is 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is :

A
4
B
5
C
6
D
10
Correct Answer: Option B

Let the speed of the stream be x km/hr. Then,

Speed downstream = (15 + x) km/hr,

Speed upstream = (15 - x) km/hr.

30 + 30 = 4 1
(15 + x) (15 - x) 2

900 = 9
225 - x2 2

9x2 = 225

x2 = 25

x = 5 km/hr.

Question 6
The speed of a boat in still water is 15 km/hr and the rate of current is 3 km/hr. The distance travelled downstream in 12 minutes is :

A
1.2 km
B
1.8 km
C
2.4 km
D
3.6 km
Correct Answer: Option D

Speed downstream = (15 + 3) kmph = 18 kmph.

Distance travelled = 18 x 12 km = 3.6 km.
60

Question 7
A man takes twice as long to row a distance against the stream as to row the same distance in favour of the stream. The ratio of the speed of the boat (in still water) and the stream is :

A
2 : 1
B
3 : 1
C
3 : 2
D
4 : 3
Correct Answer: Option B

Let man's rate upstream be x kmph.

Then, his rate downstream = 2x kmph.

 (Speed in still water) : (Speed of stream)

 = 2x + x : 2x - x
2 2

   = 3x : x
2 2

   = 3 : 1.

Question 8
A man rows to a place 48 km distant and come back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream . The rate of the stream is :

A
1 km/hr
B
1.5 km/hr
C
2 km/hr
D
2.5 km/hr
Correct Answer: Option A

Suppose he move 4 km downstream in x hours. Then,

Speed downstream = 4 km/hr.
x

Speed upstream = 3 km/hr.
x

48 + 48 = 14 or x = 1 .
(4/x) (3/x) 2

So, Speed downstream = 8 km/hr, Speed upstream = 6 km/hr.

Rate of the stream = 1 (8 - 6) km/hr = 1 km/hr.
2

Question 9
Speed of a boat in standing water is 9 kmph and the speed of the stream is 1.5 kmph. A man rows to a place at a distance of 105 km and comes back to the starting point. The total time taken by him is:

A
20 hours
B
18 hours
C
16 hours
D
24 hours
Correct Answer: Option D

Speed upstream = 7.5 kmph.

Speed downstream = 10.5 kmph.

Total time taken = 105 + 105 hours
7.5 10.5

= 24 hours.

Question 10
A man can row 7 kmph in still water. If in a river running at 1.5 km an hour, it taken him 50 minutes to row to a place and back, how far off is the place ?

A
6 km
B
9 km
C
3 km
D
4 km
Correct Answer: Option C

Speed downstream = (7.5 + 1.5) kmph = 9 kmph;

Speed upstream = (7.5 - 1.5) kmph = 6 kmph.

Let the required distance be X km. Then,

X/9 + X/6 = 50/60 
<=> 2X + 3X = 5/6 x 18 
<=> 5X = 15 
<=> X = 3 
Hence, the required distance is 3 km.
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