Question

7. Pratik takes 8 hours to travel 36 km downstream and return to the same spot. The
Pintu takes 6 days more than those of Nishu to complete certain work. If they work
speed of boat in still water is 12 km. per hour. Find the speed of water current.​

Answer 1

Answer:

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Step-by-step explanation:

ANSWER

Let the speed of the current be x km/hr.

Pratik goes 36 km downstream.

∴ Distance covered by the Pratik in Downstream =36 km.

Speed of the Pratik in downstream =(12+x) km/hr.

∴ Time taken =

(12+x)

36

Now, He also returned to the same spot.

∴ Distance covered in upstream =36 km.

Speed of the Pratik in upstream =(12−x) km/hr.

∴ Time taken =

(12−x)

36

Now,

Time taken in upstream + Time taken in downstream =8 hrs.

∴

(12−x)

36

+

(12+x)

36

=8

⇒36(12+x)+36(12−x)=8(12+x)(12−x)

⇒36(12+x+12−x)=8(144−12x+12x−x

2

)

⇒36×24=8(144−x

2

)

⇒36×3=144−x

2

∴x

2

=144−108

∴x=

36

⇒x=+6 or −6

−6 cannot be possible.

∴ Speed of the current is 6 km/hr.

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