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Question
The circumference of a circle exceeds its diameter by 18 cm. find the radius of the circle.
Solution
Let c be the circumference and d be the diameter of the circle.
∴ c = d + 18
⇒ dπ = d + 18 ⇒ dπ − d = 18
d(π − 1) = 18
⇒ `"d"(22/7-1)` = 18
⇒ `"d"(15/7) =18`
⇒ d =`(18xx7)/15=126/15` = 8.4 cm
∴ Radius =`"d"/2=8.4/2` = 4.2 cm
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