What is the diameter of a circle if its area is 78.5 cm²? (2020)

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Question: What is the diameter of a circle if its area is 78.5 cm²? (2020)

Options:

Correct Answer: 10 cm

Exam Year: 2020

Solution:

Area = πr²; 78.5 = π * r²; r² = 78.5/π; d = 2√(78.5/π) = 10 cm.

What is the diameter of a circle if its area is 78.5 cm²? (2020)

What is the diameter of a circle if its area is 78.5 cm²? (2020)

Step 1: Understand that the area of a circle is given by the formula Area = πr², where r is the radius.
Step 2: We know the area is 78.5 cm², so we can write the equation: 78.5 = π * r².
Step 3: To find r², we need to isolate it. We do this by dividing both sides of the equation by π: r² = 78.5 / π.
Step 4: Now, we need to calculate the value of r. To do this, we take the square root of r²: r = √(78.5 / π).
Step 5: The diameter (d) of the circle is twice the radius, so we use the formula: d = 2 * r.
Step 6: Substitute r into the diameter formula: d = 2 * √(78.5 / π).
Step 7: Finally, calculate the value to find the diameter: d = 10 cm.

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