In a fixed time, a boy swims double the distance along the current that he swims against the current. If the speed of the current is 3 km/h, then what is the speed of the boy in still water?

Let boy's still water speed = b km/h, current speed = c = 3 km/h. Downstream speed = b + c, upstream speed = b - c. In fixed time t: distance downstream = 2 × distance upstream (given 'swims double'). So (b + c)t = 2(b - c)t, meaning b + c = 2b - 2c. Simplify: c + 2c = 2b - b, so 3c = b. With c = 3: b = 3 × 3 = 9 km/h. Option A is correct.