Square a 3-digit number when the middle number is zero

You can quickly square a 3-digit number when the middle number (number in the tens place) is zero in about 4 seconds by following this trick.

Example #1

(604)²

Step 1

Square 6 and write it down on the left: 6² = 36

36

Step 2

Square 4 and write it down on the right side of 36: 4² = 16

36          16

Step 3

Multiply 2 by the product of the number in the ones place and the number in the hundreds place. 

2 × 6 × 4 = 48

Step 4

Write 48 between 36 and 16 and you are done.

(604)² = 364816 

Example #2

(903)²

Step 1

Square 9 and write it down on the left: 9² = 81 

81

Step 2

Square 3: 3² = 9

Since 9 is smaller than 10, put a zero on the left of it and write everything on the right side of 81.

81          09

Step 3

Multiply 2 by the product of the number in the ones place and the number in the hundreds place. 

2 × 3 × 9 = 54

Step 4

Write 54 between 81 and 09 and you are done.

(903)² = 815409