No problem, let's work through this together. We're starting with 1000 and 8409 and adding them all up.

Step 1: We'll start by adding the digits 0 & 9 in column 1 and get 9.

Step 2: We'll start by adding the digits 0 & 0 in column 2 and get 0.

Step 3: We'll start by adding the digits 0 & 4 in column 3 and get 4.

Step 4: We'll start by adding the digits 1 & 8 in column 4 and get 9.

So, 1000 + 8409 = 9409.

