Solve, using properties/ methods that simplify the calculations:
`578+999`

Answer

To solve the problem \( 578 + 999 \) using properties that simplify calculations, we can follow these steps:

### Step-by-Step Solution:

1. **Rewrite the Problem**: Start with the expression \( 578 + 999 \).

2. **Break Down 999**: Recognize that \( 999 \) can be rewritten as \( 1000 - 1 \). So, we can express the equation as:
\[ 578 + 999 = 578 + (1000 - 1) \]

3. **Use Associative Property**: According to the associative property of addition, we can rearrange the terms:
\[ 578 + (1000 - 1) = (578 + 1000) - 1 \]

4. **Calculate \( 578 + 1000 \)**: Now, add \( 578 \) and \( 1000 \):
\[ 578 + 1000 = 1578 \]

5. **Subtract 1**: Finally, subtract \( 1 \) from \( 1578 \):
\[ 1578 - 1 = 1577 \]

### Final Answer:
Thus, the solution to \( 578 + 999 \) is \( 1577 \).

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