Easy way to mentally square any number from 20 to 29.

• Step 1) First add given no. & unit digits.
• Step 2) Double the result obtained in first step.
• Step 3) Square the units digit of the number given in question & place it next to the result obtained in second step.

    e.g. 1. (23)^2
           Step 1) :- 23 + 3 = 26
           Step 2) :- 26 * 2 = 52
           Step 3) :- (3)^2 = 9..... place this result next to the result obtained in second step.
                           i.e. 529
                           So we get, (23)^2 = 529.


           2. (24)^2
           Step 1) :- 24 + 4 = 28
           Step 2) :- 28 * 2 = 56
           Step 3) :- (4)^2 = 16... place this result next to the result obtained in second step.
                    i.e. 5616...here we get result in 4 digits no. so add middle two digit for get ans.
                    = 6 + 1
                    =7...place this result in between 1st & last digit of the result obtained in 3rd step
                    i.e. 576.
                    So we get, (24)^2 = 576.

          3. (29)^2
           Step 1) :- 29 + 9 = 38
           Step 2) :- 38 * 2 = 76
           Step 3) :- (9)^2 = 81... place this result next to the result obtained in second step.
                    i.e.7681..... here we get result in 4 digits no. so add middle two digit for get ans.
                     = 6 + 8
                     =14....place 4 in between first and last digit of the result obtained in 3rd step &                              forward carry 1
                     i.e. 841
                     So we get, (29)^2 = 841.
     😊 Best luck.