the difference between the circumference and radius of a circle is 111 cm then the area of a circle.
answer : 1386
need explanation
Answers
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☆ Given :
circumference - radius = 111cm
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Procedure:
2πr - r = 111
▪︎ r(2π -1) = 111
▪︎ r = 111/(2π-1)
▪︎r = 111(2*22/7-1)
● r = 111( 44/7-1)
● r = 111( 37/7)
▪︎ r = 111* 7/37
▪︎ r = 3*7
r = 21 cm.
Diameter = 2 r
= 2*21 => 42 cm
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Area :
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Answer- The above question is from the chapter 'Areas Related to Circles'.
Concepts used: 1) Circumference of circle = 2πr
2) Area of circle = πr²
Given question: The difference between the circumference and radius of a circle is 111 cm, then the area of a circle is ____ .
Solution: Let r be the radius of a circle.
2πr - r = 111 cm
r (2π - 1) = 111
r × = 111
r × 37 = 777
r = 777 ÷ 37
r = 21 cm
Area of circle = πr²
Area of circle = × 21 × 21
Area of circle = 22 × 3 × 21
Area of circle = 1386 cm²