please help, algebra

A number is a palindrome if it reads the same way forwards and backwards.
For example, 27872 and 48484 are palindromes, but 28389 and 12541 are not.
What is the sum of all of the 5-digit palindromes?

I assume:

$\begin{array}{|l|r|r|} \hline & & \text{sum of $5$-digit palindromes} \\ \hline \text{sum until $1$-digit palindromes} & 45 & \\ \hline \text{sum until $2$-digit palindromes} & 540 & \\ \hline \text{sum until $3$-digit palindromes} & 50040 & \\ \hline \text{sum until $4$-digit palindromes} & 545040 & \\ \hline \text{sum until $5$-digit palindromes} & 50045040 & \mathbf{49500000} \\ \hline \end{array}$

Source: https://www.educative.io/edpresso/how-to-find-the-sum-of-first-n-palindromes