Let upstream speed = Su kmph
and downstream speed = Sd kmph.
Then, ...(1)
and ...(2)
Adding (1) and (2), we get :
...(3)
Subtracting (1) and (2), we get :
....(4)
Adding (3) and (4), we get : or Su = 8.
So,
⇒ Sd = 12.
∴ Speed upstream = 8 kmph,
Speed downstream = 12 kmph.
Hence, rate of current
= kmph = 2 kmph.