# Tính diện tích hình tròn có đường kính 2 dm: Cách tính và công thức

The area of a circle with a diameter of 7.2 dm is calculated as follows: 3.6 x 3.6 x 3.14 = 40.6944 (dm^2).

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## How is the area of a circle with a diameter of 7 cm calculated?

The area of a circle can be calculated using the formula A = πr^2, where A represents the area and r represents the radius of the circle. The diameter of a circle is equal to two times its radius, so we can find the radius by dividing the diameter by 2. In this case, since we have been given a diameter of 7 cm, we can find the radius by dividing 7 by 2, which gives us a radius of 3.5 cm.

Using this information, we can substitute the value of the radius into our formula for finding the area. Since π is an irrational number that cannot be expressed exactly as a decimal or fraction, it is typically approximated as 3.14 or rounded to a specific decimal place depending on the desired level of accuracy.

Therefore, to calculate the area of a circle with a diameter of 7 cm, we use the formula A = π(3.5)^2 or A = 3.14(3.5)^2 and perform the necessary calculations.

### Step-by-step calculation:

1. Divide the given diameter (7 cm) by 2 to find the radius:

2. Substitute the value of the radius into our formula for finding area:
– Area = πr^2
– Area = π(3.5)^2 (or Area = 3.14(3.5)^2 if using an approximation for π)

3. Perform the calculation:
– Area ≈ 22/7 * (3.5)^2 (or Area ≈ 3.14 * (3.5)^2 if using the approximation)
– Area ≈ 38.5 cm^2 (or Area ≈ 38.465 cm^2 if using the approximation)

Therefore, the area of a circle with a diameter of 7 cm is approximately 38.5 square centimeters (or 38.465 square centimeters if using the approximation for π).

## What is the formula to find the area of a circle when given its diameter? The formula to find the area of a circle when given its diameter is: A = π * (d/2)^2. In this formula, A represents the area of the circle and d represents the diameter. The symbol π represents pi, which is a mathematical constant approximately equal to 3.14159. To calculate the area, you need to square half of the diameter and then multiply it by pi.

A = π * (d/2)^2

### Explanation:

To find the area of a circle, you first divide the diameter by 2 to get the radius (r), since the radius is always half of the diameter. Then, you square the radius by multiplying it by itself. Finally, you multiply that result by pi to get the area. Using this formula, you can easily calculate the area of any circle when given its diameter.

Example:
If we have a circle with a diameter of 7 cm, we can use this formula as follows:
A = π * (7/2)^2
A = π * (3.5)^2
A ≈ 38.485 cm²

Therefore, using this formula, we can calculate that the area of a circle with a diameter of 7 cm is approximately 38.485 square centimeters.

## Can you calculate the area of a circle with a diameter of 7 cm using the given information?

Yes, we can calculate the area of a circle with a diameter of 7 cm. The formula to calculate the area of a circle is A = πr^2, where A represents the area and r represents the radius. In this case, we have the diameter, which is twice the radius. So, if the diameter is 7 cm, then the radius would be half of that, which is 3.5 cm.

To find the area, we substitute the value of the radius into the formula: A = π(3.5)^2.

### Step-by-Step Guide:

1. Identify that you have been given the diameter of a circle.
2. Divide the diameter by 2 to find the radius.
– In this case, divide 7 cm by 2 to get a radius of 3.5 cm.
3. Use the formula A = πr^2 to calculate the area.
– Substitute π (pi) as approximately 3.14 and square the value of the radius: (3.5)^2
4. Calculate: A = 3.14 × (3.5)^2.

Therefore, based on these calculations, we can determine the exact area of a circle with a diameter of 7 cm.

## What is the result of calculating the area of a circle with a diameter of 7 cm? The result of calculating the area of a circle with a diameter of 7 cm is approximately 38.465 square centimeters.

### Step-by-Step Calculation:

1. Calculate: (3.5)^2 = 12.25
2. Multiply by pi: 12.25 × π ≈ 38.465.

Therefore, the area of a circle with a diameter of 7 cm is approximately 38.465 square centimeters.

## Can you explain step-by-step how to find the area of a circle when its diameter is provided as 7 cm?

Certainly! Here is a step-by-step guide on how to find the area of a circle when its diameter is provided as 7 cm.

### Step-by-Step Guide:

1. Identify that you have been given the diameter of a circle.
– In this case, the diameter is given as 7 cm.
2. Divide the diameter by 2 to find the radius.
– Divide 7 cm by 2 to get a radius of 3.5 cm.
3. Use the formula A = πr^2 to calculate the area.
– Substitute π (pi) as approximately 3.14 and square the value of the radius: (3.5)^2
4. Calculate: A = 3.14 × (3.5)^2.

By following these steps, you will be able to find the accurate area of a circle when its diameter is provided as 7 cm.

Tóm lại, diện tích hình tròn có đường kính d = 7 là 38.48 dm².

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