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​If perimeters of a square, circle and equilateral triangle are same, then minimum area will be, of:​
Question

If perimeters of a square, circle and equilateral triangle are same, then minimum area will be, of:

A.

Square

B.

Circle

C.

Equilateral triangle

D.

None of these

Correct option is C

Given:
The perimeters of a square, circle and equilateral triangle are same
Let:
P=44,π=227 P = 44, \quad \pi = \frac{22}{7} \\[8pt]​​
Then:
Square:
P=4a a=444=11As=a2=112=121P = 4a \implies a = \frac{44}{4} = 11 \\[4pt]A{_s} = a^2 = 11^2 = 121 \\[12pt]​​
Circle:
P=2πr r=442×227=44×744=7Ac=πr2=227×72=227×49=154P = 2\pi r \implies r = \frac{44}{2 \times \frac{22}{7}} = \frac{44 \times 7}{44} = 7 \\[4pt]A_c = \pi r^2 = \frac{22}{7} \times 7^2 = \frac{22}{7} \times 49 = 154 \\[12pt]​​
Equilateral Triangle:
P=3a a=44314.67At=34a2=34(443)2=34×1936993.3P = 3a \implies a = \frac{44}{3} \approx 14.67 \\[4pt]A_t = \frac{\sqrt{3}}{4}a^2 = \frac{\sqrt{3}}{4}\left(\frac{44}{3}\right)^2= \frac{\sqrt{3}}{4} \times \frac{1936}{9} \approx 93.3 \\[12pt]​​
Comparison
At93.3 (minimum),As=121,Ac=154 (maximum)A_t \approx 93.3 \; (\text{minimum}), \quad \\A_s = 121, \quad \\A_c = 154 \; (\text{maximum}) \\[8pt]​​
Correct answer is (C) – Equilateral triangle
​​

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