Instant Mental Calculation of Square RootsStep 1: Learn the Squares of 0 to 9To master the system you mustlearn by heartthe squares of numbers 0 to 9, which are shown in the table below. You also need to consider the last digit of each square.

Note how the last digits for the squares of 1 and 9 are both 1.Note how the last digits for the squares of 2 and 8 are both 4.Note how the last digits for the squares of 3 and 7 are both 9.Note how the last digits for the squares of 4 and 6 are both 6.Step 2: Determine the Square RootIgnore the lasttwodigits of the number called out by the spectator and choose the memorised square which isjust lower(or equal) to the remaining number. The corresponding square root is thefirst digit. of your answerNow consider thelast digitof the number called out by the spectator. If this is 0 or 5, then you immediately know that the last digit of your answer is also 0 or 5.In all other cases, the last digit of the number called out will indicate two possible values for the last digit of the square root. For example, if the last digit is 9, then the square root may end in either 3 or 7.To determine whether the lower or higher value should be taken, multiply thefirst digitof your answer byone greater than itself. If this isgreater thanthe first part of the number called by the spectator (i.e., ignoring the last two digits), then the last digit of your answer is thelowerof the two possible values. Otherwise the last digit is the higher value.For example if the number called is 2809, the square root could be either 53 or 57. Since 5 x 6 = 30, and 28 is less than 30, the answer is 53.