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Question
Find the radius and circumference of a circle, whose area is :
(i) 154 cm2
(ii) 6.16 m2
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Solution
(i)
Area of circle = 154 cm2
`pir^2 = 154`
`r^2 = 154/pi`
`r^2 = 154/22 xx 7`
`r^2 = 7 xx 7`
r = 7 cm
∴ circumference = `2pir`
= `2 xx 22/7 xx 7`
= 44 cm
Hence 7 cm ; 44 cm
(ii)
Area of circle = 6.16 m2
`pir^2 = 6.16`
`22/7r^2 = 616/100`
`r^2 = 616/100 xx 7/22`
`r^2 = 196/100`
`r^2 = 1.96`
r = `sqrt(1.96)`
r = 1.4 m
circumference = `2pir`
= `2 xx 22/7 xx 1.4`
= 8.8 m
∴ 1.4 m; 8.8 m
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