Question

the speed of the baat in still water and the spped of riwer is 4 km / hr and 8 km​

Answer 1

Answer:

The speed of the stream is 3km/hr

Step-by-step explanation:

⇒ Let x be the speed of the stream.

⇒  Speed of the boat in still water is 8km/hr

⇒  The speed of the boat in upstream is 8−xkm/hr

⇒  The speed of the boat in downstream is 8+xkm/hr

⇒  The time taken by the boat to cover 15km= 15/8-x hr

⇒  The time taken by the boat to cover 22km= 22/8+x hr

According to the question,

⇒ 15/8-x + 22/8+x = 5

⇒  15(8+x)+22(8−x)=5(8−x)(8+x)

⇒  120+15x+176−22x=5(64−x2)

⇒  296−7x=320−5x2

⇒  5x2−7x−24=0

⇒  5x2−15x+8x−24=0

⇒  5x(x−3)+8(x−3)=0

⇒  (x−3)(5x+8)=0

⇒  x−3=0 and 5x+8=0

⇒  x=3 and x=−8/5

Speed cannot be negative.

∴  The speed of the stream is 3km/hr