`6666.009-585.999-79.989=?`

Options

A. 5000
B. 5500
C. 6500
D. 6000

Explanation

To solve the equation \( 6666.009 - 585.999 - 79.989 \) using approximation, we will follow these steps:

### Step 1: Approximate Each Number
1. **Approximate 6666.009**:
- Since the decimal part is .009, we can round down to 6666.

2. **Approximate 585.999**:
- The decimal part .999 is greater than .5, so we round up to 586.

3. **Approximate 79.989**:
- The decimal part .989 is also greater than .5, so we round up to 80.

### Step 2: Rewrite the Equation
Now, we can rewrite the equation with the approximated values:
\[ 6666 - 586 - 80 \]

### Step 3: Perform the Subtraction
1. **First, subtract 586 from 6666**:
\[ 6666 - 586 = 6080 \]

2. **Next, subtract 80 from 6080**:
\[ 6080 - 80 = 6000 \]

### Final Answer
Thus, the value of the expression \( 6666.009 - 585.999 - 79.989 \) is approximately:
\[ \boxed{6000} \]

---