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Question

The numerical values of perimeter and area of a square are equal. The length of the side of the square is :

The correct answer is
4 units

Understanding the Square Problem

We are given a problem about a specific square. The key information is that the numerical value of its perimeter is exactly the same as the numerical value of its area. We need to find the length of one of its sides.

Mathematical Representation

Let's use algebra to solve this. Let the length of the side of the square be denoted by '$s$'.

  • The formula for the area of a square is side multiplied by side, which is $s \times s = s^2$.
  • The formula for the perimeter of a square is 4 times the side length, which is $4 \times s = 4s$.

Setting Up the Equation

The problem states that the numerical value of the area is equal to the numerical value of the perimeter. So, we can set up the equation:

Area = Perimeter

$$s^2 = 4s$$

Solving for the Side Length

Now, we need to solve this equation for '$s$'.

  1. First, let's move all terms to one side to set the equation to zero:

    $$s^2 - 4s = 0$$

  2. Next, we can factor out the common term, which is '$s$':

    $$s(s - 4) = 0$$

  3. For the product of two terms to be zero, at least one of the terms must be zero. This gives us two possibilities:
    • Possibility 1: $s = 0$
    • Possibility 2: $s - 4 = 0$
  4. Let's analyze these possibilities:
    • If $s = 0$, the square would have no size, meaning both its area ($0^2 = 0$) and perimeter ($4 \times 0 = 0$) would be zero. While mathematically correct, a square typically implies a positive side length in geometry problems.
    • If $s - 4 = 0$, we can solve for '$s$' by adding 4 to both sides: $s = 4$.

Therefore, the side length '$s$' must be 4 units for the perimeter and area to be numerically equal and for the square to have a physical dimension.

Conclusion

The length of the side of the square, where its perimeter and area have equal numerical values, is 4 units. Let's check: if the side is 4 units, the area is $4^2 = 16$ square units, and the perimeter is $4 \times 4 = 16$ units. The values match.

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Important Questions from Mensuration (Teaching)

  1. The base diameter of a cylinder is 21 cm and the height is 28 cm, then:
    (A) Radius of cylinder = 10.5 cm
    (B) Volume = 12936 cm³
    (C) Curved Surface Area = 1848 cm²
    (D) Total surface area = 2541 cm²
    Which of the following is/ are correct?
    Choose the correct answer from the options given below:
  2. On the basis of the information given in the statement, which of the suggested course of action logically follows ?
    Statement : Anamika does conceptual error while solving problems on mensuration.
    Course of Action :
    (I) Teacher gives a lot of hands-on and visual practice to Anamika.
    (II) Teacher provides the scope of discussion while giving open-ended questions.
    Choose the correct option.
  3. A teacher asked the children to cut out six squares of 'one' unit each and then asked, "How many different shapes can you make using these squares? Which shape formed would have the maximum perimeter?" The least appropriate objective of this activity is
  4. A cubical tank of side 10 m is open at the top. The inner surfaces of the tank including its base are to be painted at the rate of ₹5 per square metre. Find the total cost of painting.

  5. A solid cylinder has a radius of 7 cm and height of 10 cm. Find its total surface area. (Use \(\pi = \dfrac{22}{7}\))

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