### Theory:

General rules to add decimal numbers:
Step 1: Line up the decimal numbers one by one.

Step 2: Equalize the number of decimal places by adding zeros at the rightmost side of the decimal number.

Step 3: Start adding from the rightmost digit of the decimal number as the usual addition.

Step 4: Add both decimal part and whole number part.

Step 5: Finally, put a decimal point in the answer in the same place as the numbers above it.
Example:
Add $$456.23$$ and $$56.026$$.

Here, to equalize the decimal places, add zero at the end of $$456.23$$.

$\begin{array}{l}\phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}456.230\\ \underset{¯}{+\phantom{\rule{0.147em}{0ex}}56.026}\\ \phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}512.256\end{array}$

Therefore, the addition of $$456.23$$ and $$56.026$$ is $$512.256$$.
Example:
Find the sum of $$23.592$$, $$34.467$$ and $$56.83$$.

Here, to equalize the decimal places, add zero at the end of $$56.83$$.

$\begin{array}{l}\phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}23.592\\ \phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}34.467\\ \underset{¯}{+\phantom{\rule{0.147em}{0ex}}56.830\phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}}\\ \phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}\phantom{\rule{0.147em}{0ex}}114.889\end{array}$

Therefore, the sum of $$23.592$$, $$34.467$$ and $$56.83$$ is $$114.889$$.