NDA 2025
- Exam
- NDA
- Year
- 2025
- Subject
- Mathematics
- Chapter
- Application of Derivatives
NDA 2025 · Mathematics · Application of Derivatives
A wire of length 20 cm is to be bent into a rectangle. Which of the...
A wire of length 20 cm is to be bent into a rectangle. Which of the following statements is/are correct?
I. The rectangle of the largest area is the square.
II. It is possible to form a rectangle of an area of 27 cm^2.
Select the answer using the code given below.
I. The rectangle of the largest area is the square.
II. It is possible to form a rectangle of an area of 27 cm^2.
Select the answer using the code given below.
Options
- AI only
- BII only
- CBoth I and II
- DNeither I nor II
Correct answer
A. I only
Step-by-step solution
Let the length and breadth of the rectangle be and respectively.
Given the perimeter of the rectangle is .
The area of the rectangle is .
Substituting , we get:
To find the maximum area, we can complete the square:
The maximum value of is , which occurs when .
When , .
Since , the rectangle of the largest area is a square. Thus, statement I is correct.
The maximum possible area is . It is not possible to form a rectangle of area . Thus, statement II is incorrect.
Only statement I is correct.
Answer: I only
Given the perimeter of the rectangle is .
The area of the rectangle is .
Substituting , we get:
To find the maximum area, we can complete the square:
The maximum value of is , which occurs when .
When , .
Since , the rectangle of the largest area is a square. Thus, statement I is correct.
The maximum possible area is . It is not possible to form a rectangle of area . Thus, statement II is incorrect.
Only statement I is correct.
Answer: I only