A circle has an area of 78.5 cm². What is its radius?

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Question: A circle has an area of 78.5 cm². What is its radius?

Options:

Correct Answer: 7 cm

Solution:

Area = πr², so r² = Area/π = 78.5/π ≈ 25, thus r ≈ 5 cm.

A circle has an area of 78.5 cm². What is its radius?

A circle has an area of 78.5 cm². What is its radius?

Step 1: Write down the formula for the area of a circle, which is Area = πr².
Step 2: We know the area is 78.5 cm², so we can set up the equation: 78.5 = πr².
Step 3: To find r², we need to isolate it. Divide both sides of the equation by π: r² = 78.5/π.
Step 4: Calculate 78.5 divided by π (approximately 3.14). This gives us r² ≈ 25.
Step 5: To find the radius r, take the square root of r²: r = √25.
Step 6: Calculate the square root of 25, which is 5. Therefore, the radius r is approximately 5 cm.

Area of a Circle – The area of a circle is calculated using the formula A = πr², where A is the area and r is the radius.
Solving for Radius – To find the radius from the area, rearranging the formula to r = √(A/π) is necessary.