Question

A wire $$34\,cm$$  long is to be bent in the form of a quadrilateral of which each angle is $${90^ \circ }.$$  What is the maximum area which can be enclosed inside the quadrilateral?

A. $$68\,c{m^2}$$
B. $$70\,c{m^2}$$
C. $$71.25\,c{m^2}$$
D. $$72.25\,c{m^2}$$  
Answer :   $$72.25\,c{m^2}$$
Solution :
Let one side of quadrilateral be $$x$$ and another side be $$y$$
So, $$2\left( {x + y} \right) = 34\,\,{\text{or }}\left( {x + y} \right) = 17......\left( {\text{i}} \right)$$
We know from the basic principle that for a given perimeter square has the maximum area, so, $$x = y$$  and putting this value in equation $$\left( {\text{i}} \right)$$
$$x = y = \frac{{17}}{2}$$
Area $$ = x.y = \frac{{17}}{2} \times \frac{{17}}{2} = \frac{{289}}{4} = 72.25$$

Releted MCQ Question on
Calculus >> Application of Derivatives

Releted Question 1

If  $$a + b + c = 0,$$    then the quadratic equation $$3a{x^2}+ 2bx + c = 0$$     has

A. at least one root in $$\left[ {0, 1} \right]$$
B. one root in $$\left[ {2, 3} \right]$$  and the other in $$\left[ { - 2, - 1} \right]$$
C. imaginary roots
D. none of these
Releted Question 2

$$AB$$  is a diameter of a circle and $$C$$ is any point on the circumference of the circle. Then

A. the area of $$\Delta ABC$$  is maximum when it is isosceles
B. the area of $$\Delta ABC$$  is minimum when it is isosceles
C. the perimeter of $$\Delta ABC$$  is minimum when it is isosceles
D. none of these
Releted Question 3

The normal to the curve $$x = a\left( {\cos \theta + \theta \sin \theta } \right),y = a\left( {\sin \theta - \theta \cos \theta } \right)$$        at any point $$'\theta '$$ is such that

A. it makes a constant angle with the $$x - $$axis
B. it passes through the origin
C. it is at a constant distance from the origin
D. none of these
Releted Question 4

If $$y = a\ln x + b{x^2} + x$$     has its extremum values at $$x = - 1$$  and $$x = 2,$$  then

A. $$a = 2,b = - 1$$
B. $$a = 2,b = - \frac{1}{2}$$
C. $$a = - 2,b = \frac{1}{2}$$
D. none of these

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