Question

A man swims in a river with and against water at rate of 15 km/hr and 5km/hr find the mans speed in still water and speed of river.

Answer 1

X speed of man Y speed of river
X+Y=15
X-Y=5
X=10 Y=5

Answer 2

Let the speed of the river be b and the speed of the man in still water is a.  

Given: man swims against water at 5 Km/hr which means,

                                        a – b = 5Km/hr --- (1)

man swims along with water at 15 km/hr

                                        a + b = 15Km/hr ---(2)

solving (1) and (2),

                                        a – b = 5

                                        a + b = 15

                                      2a + 0 = 20

                                        a = 20/2

                                        a = 10 km/hr

                                        b = 5 km/hr

Hence, the speed of the man in still water is 10km/hr and the speed of the river is 5Km/hr.