In the first place, length is never measured in any sort of square units, so to say the "length is 1600 meters squared" is nonsense. However presuming that you actually had worded the question correctly, namely:
What might the length of a swimming pool be if the area is 1600 m2
Then you still have a silly question because any positive real number is a correct answer to the question. Let meters be the measure of the length of the pool, then the area will be 1600 provided the width of the pool is meters.
Pretty obviously, your instructor or your text wanted you to take the square root of 1600 and come up with a nice value of 400 meters, or perhaps they were looking for 800 meters for a length with a width of 200 meters. But neither of these answers is any more valid than a length of 1600 kilometers and a 1 millimeter width or even 1 light-year long and 169.23 nanometers wide.
Tell your instructor not to ask dumb questions.
John
My calculator said it, I believe it, that settles it
