Question

plzzz answer my question fast guys
with explain........

Answer 1

Let the speed of the stream be x km/hr.

Given that speed of the boat in still water = 18km/hr.

Then the speed of the boat Upstream = (18 - x)km/hr  ----- (1)

Then the speed of the boat Downstream = (18 + x)km/hr ---- (2) 


Therefore the Upstream Time = 24/(18 - x)  ----- (3)

Therefore the Downstream Time = 24/(18 + x)  ----- (4)


Given that It takes 1 hour to go 24km upstream than to return downstream to the same spot.

$\frac{24}{18-x} + \frac{24}{18+x} = 1$

$24(18 + x) - 24(18 - x) = (18 - x)(18 + x)$

432 + 24x - 432 + 24x = 18^2 - x^2

48x = 324 - x^2

x^2 + 48x - 324 = 0

x^2 + 54x - 6x - 324 = 0

x(x + 54) - 6(x + 54) = 0

(x - 6)(x + 54) = 0

x = 6 (or) -54.

The value of x should not be negative, so x = 6.


Therefore the speed of the stream = 6km/hr.


Hope this helps!

Answer 2

Hi,

Please see the attached file!

Thanks