arithmetic - a boat covers 48 km upstream and 72 km downstream in exactly 12 hours while it covers 72 km upstream and 48 km downstream in exactly 13 hours find the speed of the current is - skillgun

Let rate upstream = x kmph and rate downstream = y kmph.
Then, 48/x + 72/x = 12 ……..(1) and 72/x + 48/x = 13 …………….(2)
By solving the above two equations
we get : x = 8 and y = 12.
.'. Speed upstream = 8 kmph,
Speed downstream = 12 kmph.
Hence, rate of current = (12 -8)/2 = 2 kmph.