Question

the speed of the boat in still water 15kmper h it can go 30 km upstrem and retutn in 4 hours 30 min find the speed of stream


​

Answer 1

Answer:

SPEED OF STREAM $= 5 KM/H$

Step-by-step explanation:

SPEED OF BOAT IN STILL WATER = 15 KM/H

SPEED OF STREAM = X

SPEED UPSTREAM = 15-X KM/H

SPEED DOWNSTREAM = 15+X KM/H

TIME TAKEN BY THE BOAT TO GO 30 KM UPSTREAM = $\frac{30}{15-X}$

TIME TAKEN BY THE BOAT TO GO 30 KM DOWNSTREAM = $\frac{30}{15+X}$

$\frac{30}{15-X}$ + $\frac{30}{15+X}$ =$4+\frac{1}{2}$

total time taken to reach the original position is 4 hours 30 minutes

= $30$ × $(\frac{1}{15-X} +\frac{1}{15+X} ) = \frac{9}{2}$

=  $\frac{15+X+15-X}{15^{2}-x^{2} } = \frac{9}{60}$

=  $\frac{30}{225-x^{2} } = \frac{3}{20}$

=  $225-x^{2} =200$

$x^{2} =25$

∴   $X = 5 KM/H$