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Question
Select the correct option from the given alternatives :
20 metres of wire is available for fencing off a flower-bed in the form of a circular sector of radius 5 metres, then the maximum area (in sq. m.) of the flower-bed is
Options
15
20
25
30
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Solution
25
Explanation:
r + r + rθ = 20m
∴ 2r + rθ = 20
∴ θ = `(20 - 2"r")/"r"`
r = 5m
Area = `1/2"r"^2theta`
= `1/2"r"^2((20 - 2"r")/"r")`
= `1/2(5)^2((20 - 10)/5)`
= 25 sq. m
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