6.

A boat running downstream covers a distance of 16 km in 2 hours while for covering the same distance upstream, it takes 4 hours. What is the speed of the boat in still water?


A. 4 km/hr B. 6 km/hr
C. 8 km/hr D. Data inadequate
Answer and Explanation
Answer: Option B
Explanation: Rate downstream = 16/2 kmph = 8 kmph.

Rate upstream = 16/4 kmph = 4 kmph.

Speed in still water = 1/2x(8 + 4) kmph = 6 kmph.

7.

The speed of a boat in still water in 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
Answer and Explanation
Answer: Option D
Explanation: Speed downstream = (15 + 3) kmph = 18 kmph.

Distance travelled = 18 x (12/60) km = 3.6 km.

8.

A boat takes 90 minutes less to travel 36 miles downstream than to travel the same distance upstream. If the speed of the boat in still water is 10 mph, the speed of the stream is:
A. 2 mph B. 2.5 mph
C. 3 mph D. 4 mph
Answer and Explanation
Answer: Option A
Explanation: Numerical Ability Questions and Answers
9.

A man can row at 5 kmph in still water. If the velocity of current is 1 kmph and it takes him 1 hour to row to a place and come back, how far is the place?

A. 2.4 km B. 2.5 km
C. 3 km D. 3.6 km
Answer and Explanation
Answer: Option A
Explanation: Speed downstream = (5 + 1) kmph = 6 kmph.

Speed upstream = (5 - 1) kmph = 4 kmph.

Let the required distance be x km.

Then, x/6 + x/4 = 1

2x + 3x = 12

5x = 12

x = 2.4 km.

10.

A boat covers a certain distance downstream in 1 hour, while it comes back in 1 hours. If the speed of the stream be 3 kmph, what is the speed of the boat in still water?

A. 12 kmph B. 13 kmph
C. 14 kmph D. 15 kmph
Answer and Explanation
Answer: Option D
Explanation: Let the speed of the boat in still water be x kmph. Then,

Speed downstream = (x + 3) kmph,

Speed upstream = (x - 3) kmph.

(x + 3) x 1 = (x - 3) x 3/2

2x + 6 = 3x - 9

x = 15 kmph.