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.
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Answer:
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so here is your answer ÷
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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