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To solve this problem, we need to calculate the area of the circle based on its diameter, which is given as 78 cm.

### Steps:
1. **Calculate the radius**:
   - The radius \( r \) of a circle is half of the diameter.
   - \( r = \frac{78}{2} = 39 \, \text{cm} \).

2. **Use the formula for the area of a circle**:
   - The area \( A \) of a circle is given by the formula:
     \[
     A = \pi r^2
     \]
   - Substituting the radius value:
     \[
     A = \pi \times (39)^2
     \]

3. **Calculate the area**:
   \[
   A = \pi \times 1521 \approx 3.1416 \times 1521 \approx 4774.65 \, \text{cm}^2
   \]

So, the area of the circle is approximately **4774.7 cm²** (rounded to 1 decimal place).

Let me know if you'd like more details or if you have any questions!

Here are five related questions:
1. What is the circumference of a circle with a diameter of 78 cm?
2. How does the area change if the radius is doubled?
3. Can you calculate the area of a semicircle with the same diameter?
4. How would the area change if the diameter were reduced by half?
5. What would the area be if the diameter was 100 cm instead of 78 cm?

**Tip**: Always double-check the units in geometry problems, especially when calculating areas, to ensure consistency.

The diameter of a circle is 78 cm. By first calculating the radius, work out the area of the circle. Give your answer in cm² to 1 decimal place.

Learn how to calculate the area of a circle with a diameter of 78 cm using geometry principles. This problem involves calculating the radius and applying the area formula A = πr². Suitable for students in Grades 6-8.

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