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Question

A window is made up of a square portion and an equilateral triangle portion above it. The base of the triangular portion coincides with the upper side of the square. If the perimeter of the window is 6 m, the area of the window in $m^2$ is ______

The correct answer is
2.06

Window Area Calculation: Perimeter and Composite Shape

The problem requires finding the area of a window composed of a square and an equilateral triangle.

Perimeter Determination

Let 's' represent the side length of the square. Since the equilateral triangle sits atop the square, sharing a side, the triangle's side length is also 's'.

The window's perimeter comprises the bottom edge of the square and the two vertical sides of the square, plus the two exposed vertical sides of the triangle.

  • Bottom side of the square: s
  • Left side (square + triangle): s + s = 2s
  • Right side (square + triangle): s + s = 2s

Wait, let's reconsider the perimeter. The perimeter is the outer boundary. This includes:

  • The bottom side of the square (length s).
  • The left side of the square (length s).
  • The right side of the square (length s).
  • The left side of the triangle (length s).
  • The right side of the triangle (length s).

Therefore, the total perimeter is the sum of these 5 sides:

Perimeter = s + s + s + s + s = 5s.

We are given that the perimeter is 6 m:

$5s = 6 \text{ m}$

Solving for the side length 's':

$s = \frac{6}{5} \text{ m} = 1.2 \text{ m}$

Area Calculation Steps

The total area of the window is the sum of the area of the square portion and the area of the equilateral triangle portion.

Square Area Calculation

The formula for the area of a square is $A_{square} = s^2$.

Using $s = 1.2$ m:

$A_{square} = (1.2 \text{ m})^2 = 1.44 \text{ m}^2$

Equilateral Triangle Area Calculation

The formula for the area of an equilateral triangle is $A_{triangle} = \frac{\sqrt{3}}{4} s^2$.

Using $s = 1.2$ m:

$A_{triangle} = \frac{\sqrt{3}}{4} (1.2 \text{ m})^2 = \frac{\sqrt{3}}{4} \times 1.44 \text{ m}^2$

$A_{triangle} = \sqrt{3} \times 0.36 \text{ m}^2$

Using the approximation $\sqrt{3} \approx 1.732$:

$A_{triangle} \approx 1.732 \times 0.36 \text{ m}^2 \approx 0.6235 \text{ m}^2$

Total Window Area

Sum the areas of the square and the triangle:

$A_{total} = A_{square} + A_{triangle}$

$A_{total} \approx 1.44 \text{ m}^2 + 0.6235 \text{ m}^2$

$A_{total} \approx 2.0635 \text{ m}^2$

Rounding to two decimal places gives the final area.

The area of the window is approximately 2.06 $m^2$.

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Important Questions from Mensuration and Geometry

  1. In the given figure, PQRS is a square of side 2 cm and PLMN is a rectangle. The corner L of the rectangle is on the side QR. Side MN of the rectangle passes through the corner S of the square.
    What is the area (in cm²) of the rectangle PLMN?
    Note: The figure shown is representative.

  2. A regular dodecagon (12-sided regular polygon) is inscribed in a circle of radius $r$ cm as shown in the figure. The side of the dodecagon is $d$ cm. All the triangles (numbered 1 to 12) in the figure are used to form squares of side $r$ cm and each numbered triangle is used only once to form a square.
    The number of squares that can be formed and the number of triangles required to form each square, respectively, are:
    Note: The figure shown is representative.

  3. Which one of the following options has the correct sequence of objects arranged in the increasing number of mirror lines (lines of symmetry)?
  4. A circle with center at $(x, y) = (0.5, 0)$ and radius $= 0.5$ intersects with another circle with center at $(x, y) = (1, 1)$ and radius $= 1$ at two points. One of the points of intersection $(x, y)$ is:
  5. During a half-moon phase, the Earth-Moon-Sun form a right triangle. If the Moon-Earth-Sun angle at this half-moon phase is measured to be $89.85^{\circ}$, the ratio of the Earth-Sun and Earth-Moon distances is closest to
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