Suppose 30 km upstream is covered in 3x hours and 40 km upstream in 4x hours, 44 km downstream is covered in 4y hours and 55 km downstream is covered in 5y hour then, 3x + 4y = 10 ......(i) 4x + 5y = 13 ......(ii) Solving (i) and (ii) we get x = 2 and y = 1 So, upstream speed =
30
3x
= 5 km/hour Downstream speed =
44
4(y)
= 11 km/hour So, speed of the boat in the still water =