Theory:

We can follow the below steps to find the square of the decimal numbers.
Step 1: Calculate the square of the given decimal number without the decimal.
 
Step 2: Put the decimal point in the obtained number such that it is twice that of the original number.
 
Note:
 
(i) If the original number contains single decimal, then the square of that number will have double decimal.
 
Number of decimals in the given number \(\times 2 = 1 \times 2 = 2\)
 
(ii) If the original number contains double decimal, then the square of that number will have four decimal.
 
Number of decimals in the given number \(\times 2 = 2 \times 2 = 4\)
Example:
Find the square of 2.6.
 
Step 1: Calculate the square of the given number without decimal.
 
(262)=26×26=676.
 
Step 2: Now, put the decimal point in the obtained number such that it is twice that of the original number.
 
That is, the given number has a single decimal, and the answer would be the double decimal.
 
2.62=6.76
 
Therefore the square of a given decimal number is 2.6 \(=\) 6.76.