A motorboat, whose speed in 250 m/min in still water goes 30000 m downstream and comes back in a total of 270 minutes. The speed of the stream is:

Question: A motorboat, whose speed in 250 m/min in still water goes 30000 m downstream and comes back in a total of 270 minutes. The speed of the stream is:

Solution:
Let,
The speed of the stream be x m/min
∴ Speed downstream = (250 + x) m/min
And speed upstream = (250 - x) m/min

Now,
30000/(250 + x) + 30000/(250 - x) = 270
⇒ 15000000/(62500 - x²) = 270
⇒ 15000000 = 16875000 - 270x²
⇒ 270x² = 1875000
⇒ x² = 6944.44
∴ x = 83.33 m/min