JEE Main 2017 — Application Of Derivatives Question with Solution
From: JEE Main 2017 (Offline)
Question
Twenty meters of wire is available for fencing off a flower-bed in the form of a circular sector. Then the
maximum area (in sq. m) of the flower-bed, is :
Choose an option
Show full solutionCorrect option: B
Correct answer
B25
Step-by-step explanation
We have
Total length = r + r + r = 20
2r + r = 20
.......(1)
A = Area = = =
A = 10r – r2
For A to be maximum
10 – 2r = 0
r = 5
For r = 5, A is maximum From (1)
= 2
A = = 25 sq. m
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