Fill in the blank
`9sq. Cm = "_________"sq. mm`

Answer

To solve the question `9 sq. cm = "_________" sq. mm`, we need to convert square centimeters to square millimeters.

### Step-by-step Solution:

1. **Understand the relationship between cm and mm**:
We know that 1 cm = 10 mm.

2. **Convert square centimeters to square millimeters**:
Since we are dealing with square units, we need to square the conversion factor.
Therefore, (1 cm)² = (10 mm)².

3. **Calculate the conversion factor**:
(1 cm)² = 100 mm².
This means 1 square centimeter is equal to 100 square millimeters.

4. **Multiply the given area in square centimeters by the conversion factor**:
We have 9 sq. cm. To convert this to square millimeters, we multiply by 100:
\( 9 \text{ sq. cm} \times 100 \text{ sq. mm/sq. cm} = 900 \text{ sq. mm} \).

5. **Fill in the blank**:
Therefore, 9 sq. cm = 900 sq. mm.

### Final Answer:
`9 sq. cm = 900 sq. mm`