square of a number between 10 & 20

 To find the square of a number between 10 & 20

 

Eg: 18² = ?

Step I: Add the number to its ones digit

             18 + 8 = 26

Step II: Multiply the Result of step I by 10.

             26 x 10 = 260

Step III: Square the ones digit number.

             8² = 64

Step IV: Add Step II & Step III.

             260 + 64 = 324

    18² = 324

 

            Eg: 13² = (13 + 3) x 10 + 3² = 160 + 9 = 169

               Eg: 17² = (17 + 7) x 10 + 7² = 240 + 49 = 289