Question

The speed of a river current is 3 km/h. A boat takes the same time to travel 12 km upstream as it does to travel 14 km downstream. What will be the speed of the boat upstream? *
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Answer 1

Answer:

39km/h ans.

Step-by-step explanation:

SOLUTION:

LET US ASSUME THAT THE REQUIRED SPEED OF THE BOAT IN STILL WATER IS X KM/H.

NOW,

THE SPEED OF A RIVER CURRENT IS 3 KM/H

SO,

WHEN THIS BOAT TRAVELS DOWNSTREAM-

NET SPEED DOWNSTREAM => (X+3) KM/H.

SO,

WHEN THIS BOAT TRAVELS UPSTREAM-

NET SPEED UPSTREAM => (X-3) KM/H.

NOW,

SPEED = DISTANCE / TIME.

THE BOAT TAKES THE SAME TIME TO TRAVEL TO 12KM UPSTREAM.

LET THE TIME TAKEN TO COVER THIS DISTANCE BE T HOURS.

(X-3) = 12/T ........ {1}

THE BOAT TAKES THE SAME TIME TO TRAVEL 14 KM DOWNSTREAM.

(X+3) = 14/T ....... {2}

NOW, DIVIDE EQUATION 1 BY EQUATION 2.

[X-3] [X+3] = [6/7]

6 (X+3) = 7 (X-3)

6X + 18 = 7X - 21

6X - 7X = -21 -18

- X = -39

:. X = 39 KM/H

HENCE, THE REQUIRED SPEED OF THE BOAT IN STILL WATER IS 39 KM/H.

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