Math, asked by mad5sparnrekarikar, 1 year ago

a boat covers 32km upstream and 36km downstream in 7hours. also it covers 40km upstream and 48km downstream in 9hours. find the speed of the boat in still water and that of stream?

Answers

Answered by rakeshranjan385
16

Let the speed of the boat in still water = x km/hr

speed of steam = y km/hr

upstream speed =x + y

downstream speed =x - y

So, according to question ---

the eqution will be -

32/x-y + 36/x+y = 7  and 

40/x-y + 48/x+y=9

by taking 1/x-y=u and 1/x+y=v

32u+36v=7

40u+48v=9

32u+36v=7*10

40u+48v=9*8

320u+360v=70

320u+384v=72

          -24v=-2

hence  v=1/12

put value of v in eq

40u+48*1/12=9

40u=9-4

u=5/40

u=1/8

now 1/x-y=1/8 =>  x-y =8

and 1/x+y=1/12  =>   x+y = 12


hence x= 10 km/hr and y = 2km/hr.

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