Question 1

The speed of a boat downstream is 15 km/hr and the speed of the stream is 1.5 km/hr. The speed of the boat upstream is?

Accepted Answer

Let the speed of boat in still water be x km/hr Then, x + 1.5 = 15 ⇒ x = 13.5 ∴ Speed upstream = (13.5 - 1.5) km/hr = 12 km/hr

Question 2

The speed of a boat in still water is 2km/hr. If its speed upstream be 1 km/hr, then speed of the stream is?

Accepted Answer

Let the speed of stream be x km/hr Then, speed upstream = (2 - x ) km/hr ⇒ 2 - x = 1 ∴ x = 1 km/hr

Question 3

A man can row downstream at 14 km/hr and upstream at 9km/hr. Man's rate in still water is?

Accepted Answer

Man's rate in still water = (14 + 9)/2 km/hr = 11.5 km/hr

Question 4

A man can row with the stream at 11 km/hr and against the stream at 8 km/hr. The speed of the stream is?

Accepted Answer

Speed of stream = (11 - 8)/2 km/hr = 1.5 km/hr

Question 5

The speed of a boat in still water is 2 km/hr. If its speed upstream be 1 km/hr, then speed of the stream is?

Accepted Answer

Speed in upstream = Speed in still water - Speed of stream. ∵ 1 = 2 - x ∴ x = 2 - 1 = 1 km/hr

Question 6

A boat goes 14 km upstream in 56 minutes. The speed of stream is 2 km/hr. The speed of boat in still water is?

Accepted Answer

∵ Speed upstream = 14 x (60/56) = 15 km/hr Speed in upstream = Speed in still water - Speed of stream. ⇒ x - 2 = 15 ∴ x = 17 km/hr

Question 7

The speed of a boat in still water is 10 km/hr. If its speed down stream be 13 km/hr, then speed of the stream is?

Accepted Answer

Speed in still water + Speed of stream = Speed in downstream. ⇒ 10 + y = 13 ∴ y = 13 - 10 = 3 km/hr

Question 8

The speed of a boat in still water is 12 km per hour. Going downstream it moves at the rate of 19 km per hour. The speed of the boat against the stream is?

Accepted Answer

Speed of stream = speed in downstream - Speed in still water ⇒ Speed of stream = 19 - 12 = 7 km/hr Speed of boat against stream = Speed in still water - Speed of stream. ⇒ Speed of boat against stream = 12 - 7 = 5 km/hr

Question 9

If a man rows at the rate of 5 km/hr in still water and his rate against the current is 3.5 km/hr, then the man's rate along the current is?

Accepted Answer

Speed of current = 5 - 3.5 = 1.5 km/hr Man's speed along the current = Man speed in still water + speed of current. ⇒ Man's speed along the current = 5 + 1.5 = 6.5 km/hr

Question 10

A man rows upstream 16 km and downstream 27 km talking 5 hours each time. What is the velocity of current?

Accepted Answer

Man's rate upstream = 16/5 km/hr Man's rate downstream = 27/5 km/hr ∴ Velocity of the current = (27/5 - 16/5)/2 km/hr = 1.1 km/hr

Question 11

A boat moves downstream at the rate of one km in 7 1/ 2 minutes and upstream at the rate of 5 km an hour. What is the velocity of current?

Accepted Answer

Rate downstream = (2/15) x 60 km/hr = 8 km/hr Rate upstream = 5 km/hr ∴ Velocity of the current = (8 - 5)/2 km/hr = 1.5 km/hr

Question 12

A person rows a kilometre down the stream in 10 minute and upstream in 30 minutes. Find the velocity of the stream?

Accepted Answer

Velocity of stream = (downstream velocity - upstream velocity)/2 = (60/10 - 60/30)/2 = 2 km/hr

Question 13

The speed of a boat downstream is 15 km/hr and the speed of the stream is 1.5 km/hr. The speed of the boat upstream?

Accepted Answer

Speed of boat in still water = 15 - 1.5 = 13.5 km/hr Speed of boat in upstream = 13.5 - 1.5 = 12 km/hr

Question 14

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 minute is?

Accepted Answer

Downstream speed = 15 + 3 = 18 km/hr. Required distance = (18 x 12)/60 = 3.6 km

Question 15

A man can row upstream 32 km in 4 hours. If the speed of current is 2 km/hr, find how much he can go downstream in 6 hours?

Accepted Answer

∵ Upstream rate = 32/4 = 8 km/hr ⇒ Speed of man in still water = 8 + 2 = 10 km/hr ⇒ Downstream rate = (10 + 2) = 12 km/hr Now, the required distance = 12 x 6 = 72 km

Question 16

A man can row upstream 36 m in 6 hours. If the speed of a man in still water is 8 km/hr, find how much he can go downstream in 10 hours?

Accepted Answer

∵ Speed of current = 8 - 36/6 = 2 km/hr ⇒ Rate downstream = (8 + 2) = 10 km/hr ∴ Required distance = (8 + 2) x 10 = 100 km

Question 17

A man can row upstream at 15 km/h and downstream at 21 km/h. The speed of water current of the river is?

Accepted Answer

Speed of water current =( Vd - Vu)/2 = (21 - 15) /2 = 3 km/h

Question 18

A man rows downstream 60 km and upstream 36 km, taking 4 hours each time. The speed of the man is :

Accepted Answer

Sd = 15 km/h Su = 9 km/h Speed of man= (Sd + Su)/2 ∴ Speed of man = (15 + 9)/ 2 = 12 km/h

Question 19

When the speed of a boat in still water is 4 km/h and the rate of stream is 2 km/h, find upstream speed of the boat.?

Accepted Answer

Upstream speed of boat = Boat's speed in still water - Rate of stream = 4 - 2 = 2 km/h

Question 20

If the speed of swimmer in still water is 9 km/h. Find the downstream speed of the swimmer, when the river is flowing with the speed of 6 km/h.?

Accepted Answer

Speed downstream = Swimmer'S speed in still water + Rate of stream = 9 + 6 = 15 km/h

Boats and Streams Questions