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Find the circumference of a circle that circumscribes a square of side 7 cm. (Use π=722.)
44 cm
222 cm
22 cm
442 cm
222 cm
For a square of side 'a' inscribed in a circle, the diagonal of the square is the diameter of the circle. Diameter = 72. Circumference = π×72=722×72=222.
Square of side length a = 7 cm is inscribed in a circle, meaning the circle circumscribes the square.
d=a2, C=πd
For a square of side 'a' inscribed in a circle, the diagonal of the square is the diameter of the circle. Diameter = 72. Circumference = π×72=722×72=222.
Confusing 'inscribed in a circle' (where diameter = diagonal) with 'circumscribed about a circle' (where diameter = side).
Identify the relationship
When a square is inscribed in a circle, the diagonal of the square is equal to the diameter of the circle (d).
d=a2
Calculate the diameter
Given the side of the square a=7 cm, we find the diagonal: d=72 cm.
d=72
Calculate the circumference
Using the circumference formula C=πd and substituting π=722 and d=72:
C=722×72=222 cm
B is correct because the diameter of the circle is the diagonal of the square (72 cm), making the circumference 222 cm.
This concept is frequently used in 'Area of Shaded Regions' problems where you subtract the area of an inscribed square from the area of the circle.