Question

A boat , whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes .what is the speed of the stream​

Answer 1

$\red{\textbf{Answer :- 5 km/hr}}$

Step-by-step explanation:

$Let \: the \: speed \: of \: the \: stream \: be \:  x km/hr$

$Then \: Speed \: of \: boat \: downstream  \: =(15+x) km/hr$

$Speed \: of \: boat \: upstream  =(15−x) km/hr$

$Therefore,$

⇒$\Large\frac{30}{15 + x} + \frac{30}{15 - x} = 4 \frac{1}{2} = \frac{9}{2}$

⇒$\Large\frac{30(15 - x) + 30(15 + x)}{(15 + x)(15 - x)} = \Large\frac{9}{2}$

⇒$\Large\frac{900}{225 - {x}^{2} } = \frac{9}{2}$

⇒$200 = 225 - {x}^{2}$

⇒${x}^{2} = 25$

⇒$x = 5 \: km/hr$

$\red{\textbf{Thus , speed of stream is 5 km/hr.}}$