Question

Please answer this question plzzz​

Answer 1

Let the speed of the stream be x,

According to the question:

☛ t + 1 = (24)/(18 - x)

☛ 18t - xt + 18 - x = 24

☛ 18t - xt - x = 6

☛ t( 18 - x ) - x = 6 ...(1)

Also,

☛ t = 24/(18 + x) ...(2)

Putting t = 24/(18 + x) in (1)

$</p><p> \sf \rightarrow \quad \: t(18 - x) - x = 6 \\ \\ \sf \rightarrow \quad \frac{24}{18 + x} \cdot (18 - x) - x = 6 \\ \\ \sf \rightarrow \quad \frac{432 - 24x - 18x - {x}^{2} }{18 + x} = 6 \\ \\ \sf \rightarrow \quad 432 - 42x - {x}^{2} = 108 + 6x \\ \\ \sf \rightarrow \quad {x}^{2} + 48x - 324 = 0 \\ \\ \sf \rightarrow \quad {x}^{2} + 54x - 6x - 324 = 0 \\ \\ \sf \rightarrow \quad x(x + 54) - 6(x + 54) = 0 \\ \\ \sf \rightarrow \quad (x + 54)(x - 6) = 0 \\</p><p>$

We get,

x = -54 and x = 6

Since, Speed can't be negative so -54 is neglected.

Hence, Speed of the stream is 6 km/h