Testing a number perfect square or not?

Answer 1

One trick for finding whether or not a number is a perfect square is to subtract a series of odd numbers from it. If you get down to exactly zero, it is a perfect square. For example:

49 - 1 = 48

48 - 3 = 45

45 - 5 = 40

40 - 7 = 33

33 - 9 = 24

24 - 11 = 13

13 - 13 = 0

Because our series of subtractions led us to the number zero, we know that 49 is a perfect square. On top of that, this technique will also tell you what it's square root is. The square root of the number will be equal to the number of subtractions required to get down to zero. In this case, we made seven subtractions, which tells us that seven is the square root of forty-nine.