Question: 1 -

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

3

5

8

9

Answer:

8

Solution:

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

Question: 2 -

 A boat can travel with a speed of 13 km/hr in still water. If the speed of the stream is 4 km/hr, find the time taken by the boat to go 68 km downstream. 

5 hours

3 hours

4 hours

2 hours

Answer:

4 hours

Solution:

Speed downstream = (13 + 4) km/hr = 17 km/hr.

Time taken to travel 68 km downstream =		68	hrs = 4 hrs.
		17

Question: 3 -

A person can swim in still water at 4 km/h. If the speed of water 2 km/h, how many hours will the man take to swim back against the current for 6km? 

Insufficient data

4 (1/2)

4

3

Answer:

3

Solution:

M = 4

S = 2

US =  4 - 2 = 2

D = 6

T = 6/2 = 3

Question: 4 -

A motorboat, whose speed in 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:

4

6

10

5

Answer:

5

Solution:

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: 5 -

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: 

10 km/hr

9 km/hr

12.5 km/hr

8.5 km/hr

Answer:

10 km/hr

Solution:

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.