The upstream speed of a boat is 12 km/hr more than the speed of a stream. If the boat can cover 45 km downstream in 2.5 hours, then how much distance is covered by the boat upstream in 5 hours?

Correct option is A

Let the speed of boat in still water and speed of stream is X and Y km/hr respectively.
(X - Y) - Y = 12
X - Y - Y = 12
X -2Y = 12
X = 12 + 2Y….(I)
And
$$\frac{45}{X + Y}$$ = 2.5
18 = X + Y
18 = 12 + 2Y + Y (From I)
6 = 3Y
2 = Y
X = 12 + 2(2)
X = 16
Required distance = 5 × (16 - 2) = 70 km