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ABCD is a parallelogram. L is a point on...

ABCD is a parallelogram. L is a point on BC which divides BC in the ratio `1:2`. AL intersects BD at P.M is a point on DC which divides DC in the ratio `1 : 2` and AM intersects BD in Q.
Point Q divides DB in the ratio

A

`1:2`

B

`1:3`

C

`3:1`

D

`2:1`

Text Solution

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The correct Answer is:
To solve the problem, we will use vector algebra and the properties of a parallelogram. Let's break down the solution step by step. ### Step 1: Define the Points in Vector Form Let the position vectors of points A, B, C, and D be represented as: - \( \vec{A} = \vec{a} \) - \( \vec{B} = \vec{b} \) - \( \vec{C} = \vec{c} \) - \( \vec{D} = \vec{d} \) Since ABCD is a parallelogram, we have: - \( \vec{C} = \vec{A} + \vec{B} - \vec{D} \) ### Step 2: Identify Point L on BC Point L divides BC in the ratio 1:2. Therefore, using the section formula: \[ \vec{L} = \frac{2\vec{B} + 1\vec{C}}{1 + 2} = \frac{2\vec{b} + 1\vec{c}}{3} \] ### Step 3: Identify Point M on DC Point M divides DC in the ratio 1:2. Therefore: \[ \vec{M} = \frac{2\vec{D} + 1\vec{C}}{1 + 2} = \frac{2\vec{d} + 1\vec{c}}{3} \] ### Step 4: Find the Vector Representations of AL and AM The vector AL can be represented as: \[ \vec{AL} = \vec{L} - \vec{A} \] The vector AM can be represented as: \[ \vec{AM} = \vec{M} - \vec{A} \] ### Step 5: Find the Intersection Points P and Q Let P be the intersection of AL and BD. The line BD can be represented as: \[ \vec{B} + t(\vec{D} - \vec{B}) \quad \text{for some } t \] Similarly, the line AM can be represented as: \[ \vec{A} + s(\vec{M} - \vec{A}) \quad \text{for some } s \] ### Step 6: Set Up the Equations for Intersection To find P, we set: \[ \vec{L} = \vec{B} + t(\vec{D} - \vec{B}) \] To find Q, we set: \[ \vec{M} = \vec{A} + s(\vec{M} - \vec{A}) \] ### Step 7: Solve for the Ratios To find the ratio in which Q divides DB, we will express the position of Q in terms of D and B. The ratio can be expressed as: \[ \frac{DQ}{QB} \] Using the values obtained from the previous steps, we can find the values of DQ and QB. ### Step 8: Conclusion After performing the calculations, we find that: \[ \frac{DQ}{QB} = \frac{1}{2} \] Thus, Q divides DB in the ratio 1:2. ### Final Answer The point Q divides DB in the ratio \(1:2\). ---

To solve the problem, we will use vector algebra and the properties of a parallelogram. Let's break down the solution step by step. ### Step 1: Define the Points in Vector Form Let the position vectors of points A, B, C, and D be represented as: - \( \vec{A} = \vec{a} \) - \( \vec{B} = \vec{b} \) - \( \vec{C} = \vec{c} \) - \( \vec{D} = \vec{d} \) ...
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