1. Man can row 30km upstream & 44km downstream in 10 hrs. Also he run 40km upstream & 55km downstream in 13 hrs. Find the rate of the current & the speed of the man in still water ?

A) 3 & 8 km/hr

B) 2 & 5 km/hr

C) 1 & 3 km/hr

D) None of the above

Ans. A

Upstream Downstream time

30 44 10

40 55 13

Upstream = 30*55 – 40*44 / 44*13 – 55*10 = 5

Downstream = 30*55 – 40*44 / 30*13 – 40*10 = 11

Therefore, Rate of current = 11-5/2 = 3 km/hr

Speed of the man = 11+5/2 = 8 km/hr

2. A motor boat takes 2 hrs to travel a distance of a 9km down the current & it takes 6 hrs. to travel the same distance against the current. The speed of the boat(in km/hr) in still water & that of the current are

A) 3,2

B) 3,1

C) 3.5,2.5

D) 3,1.5

Ans. D

Let speed of boat in still water be x km/hr & speed of current be y km/hr

9/x+y = 2

& 9/ x-y =6

X+y=9/2

x-y = 9/6 = 3/2

therefore, x=3 & y=1/2 km/hr

3. A boat can travel with a speed of 16 km/hr in still water. If the rate of stream is 5 km/hr, then find

the time taken by the boat to cover distance of 84 km downstream.

A) 4 hours

B) 5 hours

C) 6 hours

D) 7 hours

Ans. A

Speed downstream = (16 + 5) = 21 kmph

Time = distance/speed = 84/21 = 4 hours

4. A man can row at 5 kmph in still water. If the velocity of the current is 1 kmph and it takes him 1 hour

to row to a place and come back. how far is that place.

A) 0.4 km

B) 1.4 km

C) 2.4 km

D) 3.4 km

Ans. C

Let the distance is x km

Rate downstream = 5 + 1 = 6 kmph

Rate upstream = 5 – 1 = 4 kmph

then

x/6 + x/4 = 1 [because distance/speed = time]=> 2x + 3x = 12

=> x = 12/5 = 2.4 km

5. 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) 1.6 km

B) 2 km

C) 3.6 km

D) 4 km

Ans. C

Speed downstreams =(15 + 3)kmph

= 18 kmph.

Distance travelled = (18 x 12/60)km

= 3.6km

iibm

Wow, fantastic weblog format! How lengthy have you been running a blog for?

you make running a blog glance easy. The total glance of your site is excellent, let alone the content material!

You can see similar here sklep online

Wow, fantastic weblog layout! How lengthy have you been blogging for?

you make running a blog glance easy. The total look of your site

is fantastic, let alone the content! You can see similar here sklep internetowy