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Question

A rectangle becomes a square when its length and breadth are reduced by 10 m and 5 m, respectively. During this process, the rectangle loses 650 m² of area. What is the area of the original rectangle in square meters?

The correct answer is
2250

Rectangle Reduction Scenario

We are given a rectangle. When its length is decreased by 10 m and its breadth by 5 m, it transforms into a square. This transformation also results in a loss of 650 m² from the original area.

Equations from Conditions

Let the original length of the rectangle be $L$ meters and the original breadth be $B$ meters.

The original area of the rectangle is $A_{orig} = L \times B$. After the reductions, the new length is $L-10$ and the new breadth is $B-5$. Since the new shape is a square, its sides must be equal:

$ L - 10 = B - 5 \quad (1) $

The new area is $A_{new} = (L-10)(B-5)$. The problem states that the area loss is 650 m²:

$ A_{orig} - A_{new} = 650 $ $ (L \times B) - (L-10)(B-5) = 650 \quad (2) $

Dimensions Solved

We solve the system of equations to find the original dimensions:

  1. From equation (1), we express $L$ in terms of $B$: $ L = B - 5 + 10 $ $ L = B + 5 $
  2. Substitute this expression for $L$ into equation (2): $ ((B+5) \times B) - ((B+5-10) \times (B-5)) = 650 $ $ (B^2 + 5B) - ((B-5) \times (B-5)) = 650 $
  3. Expand and simplify the equation: $ (B^2 + 5B) - (B^2 - 10B + 25) = 650 $ $ B^2 + 5B - B^2 + 10B - 25 = 650 $ $ 15B - 25 = 650 $
  4. Solve for $B$: $ 15B = 650 + 25 $ $ 15B = 675 $ $ B = \frac{675}{15} $ $ B = 45 \text{ m} $
  5. Calculate $L$ using $L = B + 5$: $ L = 45 + 5 $ $ L = 50 \text{ m} $

Original Area Calculation

Now, calculate the area of the original rectangle using the found dimensions $L=50$ m and $B=45$ m:

$ \text{Original Area} = L \times B $ $ \text{Original Area} = 50 \text{ m} \times 45 \text{ m} $ $ \text{Original Area} = 2250 \text{ 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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