MCQ
Among all the parallelograms whose diagonals are $10$ and $4$,the one having maximum area has its perimeter lying in the interval
  • A
    $(19,20]$
  • B
    $(20,21]$
  • $(21,22]$
  • D
    $(22,23]$

Answer

Correct option: C.
$(21,22]$
c
(c)

Area of parallelogram whose diagonals are 10 and 4 and if angle between adjacent side is $\theta$ is

$A=\frac{10 \times 4}{\sin \theta}$

The area will be maximum if $\theta=\frac{\pi}{2}$, so the parallelogram must be rhombus

Perimeter of rhombus

$=4 \sqrt{2} \overline{9}=\sqrt{46} \overline{4} \text { and } \sqrt{46} \overline{4} \in(21,22]$

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