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Time taken to cover 30 km upstream =

Total time taken = hrs.

According to the given condition

2
600 = 3(225 - x )
2
600 = 675 - 3x
2
- 75 = - 3x
2
x - 25 = 0
(x+5)(x-5)= 0
X = -5 or x= 5
but x= - 5 is not possible as speed can not be negative.
Hence , Speed of the stream is 5 km/h.

Example 7: Solve the quadratic equation by factorisation method:

Ans: The given equation is

-ab(a + b) = (a + b)x(a + b + x)
(a + b) [x(a + b + x) + ab] = 0
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