Solve the Decimal Addition: Finding the Sum of 1.3 + 1.1

To solve this problem, let's follow these steps to perform decimal addition:

• Step 1: Align the decimal points of numbers $1.3$ and $1.1$.

• Step 2: Add the numbers starting from the right, moving towards the left.

Now, let's perform the calculation:

Align the numbers:
$\begin{aligned} &{1.}3 \\ +&1.1 \\ \hline \end{aligned}$

Step 1: Add the digits in the tenths place: $3 + 1 = 4$.

Step 2: Add the digits in the units place: $1 + 1 = 2$.

Combine these results to find the total sum: $2.4$.

Therefore, the solution to the problem is $2.4$, which corresponds to choice 4.