Any number that is less than 2 will work. It is impossible to find the square root of a negative number (you can only get imaginary number) since anything square is a positive number. PS. If you are confused by the answer, just ask me.
If it took 4 miles per hour you multiply that twice cuss its traveling back then forth so you repeat the same process 30 miles times 2 which is 60 hope this helps.