Question

If a motor boat can travel 30 km upstream and 28 downstream in 7h it can travel 21 km upstream and return in 5h find the speed of boat in still water and the speed of the stream

PLZ answer fast and give step to step explaination​

Answer 1

Answer:

Step-by-step explanation:

let he speed of boat be "x" and the speed of stream be"y"

* for upstream the speed will be = x-y

* for downstream the speed will be= x+y

according to the information-:

30/x-y + 28/x+y = 7  -------------(eq 1)

21/x - y + 21/x + y = 5   ---------(eq 2)

let :-

1/x-y= a          and           1/x+y = b

therefor the above equation will be changed to:-

30a + 28b = 7

21a + 21b = 5    

on solving both the equation:-

a=1/6

b=1/14

now we know that

a= 1/x-y            and           b = 1/x+y

x - y = 6 ---- (eq 3)

x + y = 14 --------(eq4)

from solving eq -3 and eq- 4

x=10 (speed of boat)

y= 4( speed of stream)