### Theory:

Objective:

To find a square of the decimal number.

We can follow the below steps to find out the square of the decimal numbers.
Step 1: First 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 be double decimal. $\mathit{Number}\phantom{\rule{0.147em}{0ex}}\mathit{of}\phantom{\rule{0.147em}{0ex}}\mathit{decimals}\phantom{\rule{0.147em}{0ex}}\mathit{in}\phantom{\rule{0.147em}{0ex}}\mathit{the}\phantom{\rule{0.147em}{0ex}}\mathit{original}\phantom{\rule{0.147em}{0ex}}\mathit{number}\phantom{\rule{0.147em}{0ex}}×2=1×2=2$

ii) If the original  number contains double decimal, then the square of that number will have four decimal.

$\mathit{Number}\phantom{\rule{0.147em}{0ex}}\mathit{of}\phantom{\rule{0.147em}{0ex}}\mathit{decimals}\phantom{\rule{0.147em}{0ex}}\mathit{in}\phantom{\rule{0.147em}{0ex}}\mathit{the}\phantom{\rule{0.147em}{0ex}}\mathit{original}\phantom{\rule{0.147em}{0ex}}\mathit{number}\phantom{\rule{0.147em}{0ex}}×2=2×2=4$
Find out the square of 7.4.

Apply the theory mentioned above.

Step 1: Calculate the square of the given decimal number.

${\left(74}^{2}\right)=74×74=5476$.

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 then the answer would be double decimal.

${7.4}^{2}=54.76$.

Therefore the square of a given decimal number is 7.4 $$=$$ 54.76.

So using the above method, we can easily find the square of decimal numbers.