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Question

The length and breadth of a rectangle is 6 cms and 8 cms respectively. Then what will be the area of a square whose side is equal to the length of the diagonal of this rectangle.

This question was previously asked in
RRB ALP 2018 CBT 2 Fitter Question Paper (21-Jan-2019) (Shift 3)
The correct answer is

100 cm2

Calculating Area of Square from Rectangle Diagonal

The problem asks us to find the area of a square whose side is equal to the length of the diagonal of a given rectangle. We are provided with the dimensions of the rectangle: length and breadth.

Let's first identify the given information:

  • Length of the rectangle = 6 cm
  • Breadth of the rectangle = 8 cm

Finding the Diagonal of the Rectangle

The diagonal of a rectangle forms a right-angled triangle with the length and breadth as the other two sides. We can use the Pythagorean theorem to find the length of the diagonal. The Pythagorean theorem states that in a right-angled triangle, the square of the hypotenuse (the diagonal in this case) is equal to the sum of the squares of the other two sides (length and breadth).

Let $d$ be the length of the diagonal of the rectangle, $l$ be the length, and $b$ be the breadth.

According to the Pythagorean theorem:

$$d^2 = l^2 + b^2$$

Substituting the given values:

$$d^2 = (6 \text{ cm})^2 + (8 \text{ cm})^2$$

$$d^2 = 36 \text{ cm}^2 + 64 \text{ cm}^2$$

$$d^2 = 100 \text{ cm}^2$$

To find the length of the diagonal $d$, we take the square root of both sides:

$$d = \sqrt{100 \text{ cm}^2}$$

$$d = 10 \text{ cm}$$

So, the length of the diagonal of the rectangle is 10 cm.

Determining the Side of the Square

The problem states that the side of the square is equal to the length of the diagonal of this rectangle. Therefore,

Side of the square = Length of the diagonal = 10 cm.

Calculating the Area of the Square

The area of a square is calculated by squaring the length of its side. Let $s$ be the side of the square.

Area of the square = $s^2$

Substituting the side length we found:

Area of the square = $(10 \text{ cm})^2$$

Area of the square = $10 \times 10 \text{ cm}^2$$

Area of the square = $100 \text{ cm}^2$$

Thus, the area of the square is 100 cm$^2$.

Summary of Steps

Step Description Calculation Result
1 Identify dimensions of the rectangle Length = 6 cm, Breadth = 8 cm -
2 Calculate the diagonal of the rectangle using Pythagorean theorem $d = \sqrt{6^2 + 8^2}$ 10 cm
3 Determine the side of the square Side = Diagonal length 10 cm
4 Calculate the area of the square Area = Side$^2$ 100 cm$^2$

The final calculated area of the square is 100 cm$^2$.

Revision Table: Rectangle and Square Properties

Shape Properties Formulas
Rectangle Four sides, opposite sides equal and parallel, four right angles (90°). Area = Length × Breadth
Perimeter = 2 × (Length + Breadth)
Diagonal = $\sqrt{\text{Length}^2 + \text{Breadth}^2}$
Square Four equal sides, four right angles (90°). A square is a special type of rectangle. Area = Side × Side = Side$^2$
Perimeter = 4 × Side
Diagonal = Side $\times \sqrt{2}$

Additional Information: Pythagorean Theorem Explained

The Pythagorean theorem is a fundamental relation in Euclidean geometry among the three sides of a right-angled triangle. It states that the area of the square whose side is the hypotenuse (the side opposite the right angle) is equal to the sum of the areas of the squares whose sides are the other two sides (the legs).

If a right-angled triangle has sides of lengths $a$ and $b$ (the legs) and the hypotenuse has length $c$, the theorem can be written as:

$$a^2 + b^2 = c^2$$

In our problem, the length and breadth of the rectangle are the legs ($a=6$, $b=8$), and the diagonal is the hypotenuse ($c=d$). We used this theorem to find the length of the diagonal, which was then used as the side of the square to calculate its area.

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