How to Solve Boats and Stream Maths Quickly

Extending from the basic knowledge rules of boats and stream math problems, here we have given some examples on how to solve boat and stream math problems quickly and easily using quick tricks and basic methods too. The aim is to give you knowledge of basic rules and math shortcut tricks to prepare you for all kind of competitive exams.

• What time will be taken by a boat to cover a distance of 128 km along the stream, if speed of boat in still water is 24 km/h and speed of stream is 8 km/h?

Answer: Here we have

B = 24 and S = 8.

So, D = 24 + 8 = 32

Since the boat is moving along the stream, it means the boat is moving downstream.

Therefore, 128/32 = 4 is the required time.

• A boat goes 48 km downstream in 20 hour. It takes 4 hour more to cover the same distance against the stream. What is the speed of the boat in still water?

Answer: From the question we have

Downstream speed of the boat = 48/20 = 2.4

And Upstream speed of the boat is 48/24 = 2.

Therefore, the speed of the boat in still water = (2 + 2.4) / 2 = 2.2 km/h.

• Ashutosh can row 24 km/h in still water. It takes him twice as long to row up as to row down the river. Find the rate of Stream.

Answer: Let’s consider that, Ashotosh takes 1 unit of time to row downstream and 2 units of time to row upstream.

Here we see that Boat’s speed is 3/2. But in question we have been given that the boat’s speed is 24 km/h.

Therefore we can write 24 * 1/3/2 = 24 * 2/3 = 16 unit.

So from the figure we can write

Downstream speed = 16 * 2 = 32 km/h.

Again,

 D = B + S

32 = 24 + S

S = 8 km/h.

• A motor boat can travel at 10 km/h in still water. It travelled 91 km downstream in a river and then returned to the same place, taking altogether 20 hour. The rate of flow of river is how much?

Answer: We know that upstream speed is

U = boat’s speed (B) – speed of the current (S)

And downstream speed is

D = boat’s speed (B) + speed of the current (S)

Therefore,

Placing B = 10, i.e. motorboat’s speed, we get

10² – S² = 91

S (rate of river flow) = 3 km/h.