If a circle has an area of 78.5 cm², what is its radius?

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Question: If a circle has an area of 78.5 cm², what is its radius?

Options:

Correct Answer: 7 cm

Solution:

Area = πr², so r = √(Area/π) = √(78.5/π) ≈ 5 cm.

If a circle has an area of 78.5 cm², what is its radius?

If 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 by π: r² = 78.5 / π.
Step 4: Now, we need to find the value of π. Use approximately 3.14 for π.
Step 5: Calculate 78.5 / 3.14 to find r²: r² ≈ 25.
Step 6: To find r, take the square root of r²: r = √25.
Step 7: Calculate the square root of 25, which is 5.
Step 8: Therefore, the radius of the circle 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.
Square Root Calculation – Finding the radius involves taking the square root of the area divided by π.