Question

A Boat goes downstream from one part of the river to another part of river in 16 hours it covers the same distance upstream in 20 hours if the speed of stream is 2 km per hour find the speed of boat in still water and distance between the two part of river

Answer 1

Speed of stream = 2 km/hr

let speed of boat (in still water) = x km/hr

while going downstream  his speed = x+2 km/hr

and going upstream = x-2 km/hr

now A/Q 

dis /x+2 = 7⇒ dis = 7 (x+2)  ......(1)

and dis / x-2 = 8 ⇒ dis = 8(x-2)  ............(2)

(1) =  (2)

7x + 14= 8x - 16  ⇒ x = 30 km/hr

and dis = 7(30+2) = 7 x 32 = 224 km

hope this helps....

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Answer 2

Step-by-step explanation:

let the speed of boat is 's' and distance is 'd'

speed of boat in downstream is (s +2)

speed of boat in upstream is (s-2)

time taken for downstream is 16hours

time taken for upstream is 20 hours

now

time for downstream = d/s+2.

16 hours. = d/s+2

16(s+2) = d

16s + 32 = d...............(I)

time for upstream = d/s-2

20. = d/s-2

20(s - 2). = d

20s - 40 = d.............(ii)

comparing eq(I) and (ii) we have

16s+32 = 20s-40

16s - 20s= -40-32

-4s. =-72

s. = -72/-4

s. = 18

putting the value of s in eq(I)

16s + 32 = d

16*18 + 32 = d

288 + 32 = d

320km = d