Common chord

Two circles with radii 18 cm and 20 cm intersect at two points. Their common chord is 11 cm long. What is the distance between the centres of these circles?

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You need to know the following knowledge to solve this word math problem:

arithmetic

square root

planimetry

Pythagorean theorem
right triangle
circle
triangle
chord

Grade of the word problem

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practice for 14 year olds

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