Solve the Addition Equation: 1000 + □ = 1001

To solve the equation $1000 + \Box = 1001$, we need to determine what number, when added to 1000, results in 1001.

Let's work through the solution with a simple subtraction method:

• Step 1: We know that $1000 + \Box = 1001$, and we need to find $\Box$.
• Step 2: We can rearrange this equation to find $\Box$ by subtracting 1000 from both sides of the equation. This gives:

$\Box = 1001 - 1000$

• Step 3: Perform the subtraction:

$\Box = 1$

Therefore, the missing number is $1$.