Question

Question 2 (i)
Formulate the following problems as a pair of equations, and hence find their solutions:
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.

Answer 1

Let the speed of Ritu in still water and the speed of stream be x km/h and y km/h respectively.
Speed of Ritu while rowing;
Upstream = (x - y) km/h
Downstream = (x + y) km/h
According to question,
2(x + y) = 20
$\Rightarrow$ x + y = 10 ... (i)
2(x - y) = 4
$\Rightarrow$ x - y = 2 ... (ii)
Adding equation (i) and (ii), we get
2x = 12
$\Rightarrow$ x = 6
Putting the value of x in equation (i), we get
x + y = 10
$\Rightarrow$ 6 + y = 10
$\Rightarrow$ y = 4
Hence, Ritu's speed in still water is 6 km/h and the speed of the current is 4 km/h.