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The distance around a circle is its _________.

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To find area, any side of a parallelogram can be chosen as _________ of the parallelogram.

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Perpendicular dropped on the base of a parallelogram from the opposite vertex is known as the corresponding _________ of the base.

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Ratio of the circumference of a circle to its diameter is denoted by symbol ________.

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If area of a triangular piece of cardboard is 90 cm², then the length of altitude corresponding to 20 cm long base is _________cm.