Question

for going 60km down stream and coming back , a boat takes 9 hours if the speed of the boat in still water is 15km/hr. find the speed of the current of water?
this que is from quadratic equation lesson plz give correct ans n explained ans​

Answer 1

Lets speed of boat = x km/hr

and speed of current = y km/hr

So while going upstream speed of man = x-y km/hr

and while going downstream =  x+y km/hr

A/Q : 4/x+y = 2  ⇒ 2x + 2y = 4 ⇒ x+y = 2  ⇒ y = 2-x ..........(1)

And  4 /x-y = 4 ⇒ x-y = 1 from (1)

x-(2-x) = 1 ⇒ 2x - 2 = 1  ⇒ x = 3/2    and so y = 1/2

Hence speed of boat = 1.5 km/hr (in still water)

speed of current = 0.5 km/hr

Answer 2

Step-by-step explanation:

Let speed of stream be xkm/hr

⇒ Downstream speed =(15+x)km/hr

⇒ Upstream speed =(15−x)km/hr

∴

15+x

30

+

15−x

30

=4

2

1

⇒

225−x

2

900

=

2

9

⇒ 9x

2

=225

⇒ x

2

=25

∴ x=5

∴ Speed of stream is 5km/hr.