Question

A man can row upstream at 12 km/hr and downstream at 18 km/hr. The man's rowing speed in still water is

A) 15 km/hr B) 5 km/hr C) 3 km/hr D) 10 km/hr

Answer 1

Answer:

Option (A) - 15 km/hr

Step-by-step explanation:

Let the speed of boat in still water = x km/h

Let the speed of boat in stream water = y km/h

Speed of boat downstream = (x+y) km/hr = 18 km/h

Speed of boat upstream = (x -y) km/h = 12 km/h

x + y = 18   ...   (i)                                          

x - y = 12   ...   (ii)

(i) + (ii), we get

2x + 0 = 30

⇒ x = 30 ÷ 2

⇒ x = 15 km/h

Using  x = 15 in (ii),

15 - y = 12

y = 15 - 12

y = 3 km/h

So, the speed of boat in still water = x = 15 km/h

Answer 2

Answer:

The answer is 15km/ h.

Step-by-step explanation:

speed in upstream=12 km/h

speed in downstream =18 km/h

speed in upstream means ,

speed of the boat in still water-speed of the stream

Let it be x and y and as per[ eq.1]=x-y=12

similarly, speed of boat in downstream=x+y=18 [eq 2]

adding both,

2x=30

x=30÷2 =15 km/h.

Dear friend I hope this answer would help you..Thanks for asking.