1.

Rectangle ABCD has area 200. An ellipse with area 200pi passes through A and C and has foci at B and D. If the perimeter of the rectangle is P. Then the value of (P)/(20) is

Answer»

2
4
8
None of these

Solution :`y^(2)=(r-X)^(2)-x^(2)`
`((r)/(2)+x)^(2)=((r)/(2)-x)^(2)+y^(2)`
`therefore 2rx=r^(2)-2rx`.
`x=(r)/(4)`
Given 2. `PI.((r)/(4))^(2)+pi.((r)/(2))^(2)=120implies(3pir^(2))/(8)=120`
Req.Area =`(1)/(2).pir^(2)-(2.pi.((r)/(4))^(2)+pi.((r)/(2))^(2))=(pir^(2))/(8)=40`


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