Question

8
2(3x + y) 2(3x - y)
2. Formulate the following problems as a pair of equations, and hence find their solutions:
(i) Ritu can row downstream 20 km in 2 hours, and upstream 4 km in 2 hours. Find her
speed of rowing in still water and the speed of the current.
2 women and 5 men​

Answer 1

Answer:

Step-by-step explanation:

Let the speed of rowing in still water be x

and speed of current be y

Speed upstream = x+y

Speed downstream = x-y

so x+y = 20/2 = 10 ------------ (1)

and x-y = 4/2 = 2 ----------------(2)

Solve (1) and (2)

x = 6km/hr

y= 4km/hr

Speed of rowing in still water = 6km/hr

Speed of current = 4km/hr

Answer 2

Given :   Ritu can row downstream 20 km in 2 hours, and upstream 4 km in 2 hours.  

To find : speed of rowing in still water and the speed of the current.

Solution:

Let say Speed of Rowing in Still water  = B  km/hr

Speed of Current  = S  km/hr

Speed Down  Stream =  B + S  km/hr

Speed UpStream  = B - S  km/hr

Distance  =  Speed * Time

Ritu can row downstream 20 km in 2 hours

=> 20  = (B + S) * 2

=> B  + S  = 10

upstream 4 km in 2 hours.  

=> 4  = (B - S) * 2

=> B - S  = 2

B  + S  = 10

B - S  = 2

Adding both

=> 2B = 12 => B = 6

& S = 4

speed of rowing in still water = 6 km/hr

speed of the current.  = 4 km/hr

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