Question

A boat goes 64 km up stream &: 72 Km down stream in 14hrs.
It goes 80 Km up stream & 96 Km downstream in 18 hrs.Find
the speed of boat in still water & the speed of the stream.

Answer 1

Answer:

Let the speed of boat in still water be x and speed of stream be y

x−y

64

+

x+y

72

=14

x−y

80

+

x+y

96

=18

Let x−y=a and x+y=b

⇒

a

64

+

b

72

=14 .....(1)

a

80

+

b

96

=18 .....(2)

Multiply eqn(1) by 4 and eqn(2) by 3

⇒

a

256

+

b

288

=56

a

240

+

b

288

=54

By subtracting the above equations, we get

a

256−240

=56−54=2

⇒

a

16

=2

∴2a=16 or a=

2

16

=8

Again,

a

240

+

b

288

=54

⇒

8

240

+

b

288

=54

⇒

b

288

=54−30=24

⇒b=

24

288

=12

∴b=x+y=12 and a=x−y=8

a+b=x+y+x−y=12+8

⇒2x=20 or x=

2

20

=10 kmper hr.

⇒x+y=12⇒y=12−x=12−10=2 kmper hr.

∴ speed of the boat in still water be 10 km per hr and speed of the stream be 2 kmper hr

Step-by-step explanation:

follow and like

Answer 2

$speed \: of \: boat \: is \: 10km \: {per \: hour} \\ and \: waters \: speed \: is \: 2km \: per \: hour$