Question

A boat can cover 14 km upstream and 21 km downstream together in 3 hours.
Also it can cover 21 km upstream and 42 km downstream together in 5 hours.
What is the speed of current?​

Answer 1

Answer:A boat can cover 21 km in the direction of current and 15 km against the current in 3 ... A boat can cover 40 km upstream and 60 km downstream together in 13 hours. ... A boat can row to a place 56 km away and come back in 22 hours. ... Find the ratio of boat in still water to speed of stream. A) 9 : 2. B) 8 : 3

Step-by-step explanation:

Answer 2

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✿ Required Answer:

✒ GiveN:

• Boat can cover 14 km upstream and 21 km downstream in 3 hours.
• Boat can cover 21 km upstream and 42 km downstream in 5 hours

✒ To FinD:

• Speed of the current.....?

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✿ How to solve?

When a body moves against the current or stream, their relative speed is their difference. And, when it moves along the current or stream, then their relative speed is their sum. So, By using this principle, ☃️ Let's solve this question....

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✿ Solution:

Let,

• Speed of the boat = x
• Speed of the current = y

[ As, the boat is moving, we can say that speed of boat is greater than stream of current Otherwise, it might have pushed backwards by the current.]

Then,

• Upstream speed = x - y
• Downstream speed = x + y

We know☘,

$\large{ \because{\boxed{ \sf{ \dfrac{Distance}{Speed} = Time}}}}$

Then,

• Time taken to cover 14 km upstream = 14 / x - y hours
• Time taken to cover 21 km downstream = 21 / x + y hours

But total journey is 3 hours,

➝ 14/x - y + 21/x + y = 3........(1)

And, also given

• Time taken to cover 21 km upstream = 21/ x - y hours
• Time taken to cover 42 km downstream = 42/ x + y hours

But total journey is 5 hours,

➝ 21/x - y + 42/x + y = 5.........(2)

Putting 1/x - y = a and 1/x + y = b

➝ 14a + 21b = 3.......(1)

21a + 42b = 5......(2)

Multiplying eq.(1) with 2

➝ 2(14a + 21b) = 6

➝ 28a + 42b = 6

Subtracting eq.(2) from eq.(1),

➝ 28a + 42b - 21a - 42b = 6 - 5

➝ 7a = 1

➝ a = 1/7

Putting value of a in eq.(1),

➝ 14 × 1/7 + 21b = 3

➝ 2 + 21b = 3

➝ 21b = 1

➝ b = 1/21

Then,

• x - y = 7
• x + y = 21

So, adding these equations,

➝ 2x = 28

➝ x = 14 km/hr

Then,

➝ 14 - y = 21

➝ y = 7 km/hr

So, Final answer:

• Speed of the boat = 14 km/hr
• Speed of the current = 7 km/hr

☀️ Hence, solved !!

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