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If the line \(2 x+y=k\) passes through the point which divides the line segment joining the points \((1,1)\) and \((2,4)\) in the ratio \(3: 2\), then \(k\) equals : (a) \(\frac{29}{5}\) (b) 5 (c) 6 (d) \(\frac{11}{5}\)

Short Answer

Expert verified
The value of \(k\) is 6.

Step by step solution

01

Calculate the coordinates of the dividing point

We need to find the coordinates of the point dividing the line segment from \((1,1)\) to \((2, 4)\) in the ratio \(3:2\). Use the section formula for internal division:\[(x, y) = \left(\frac{m_2 x_1 + m_1 x_2}{m_1 + m_2}, \frac{m_2 y_1 + m_1 y_2}{m_1 + m_2}\right)\]Substitute the values: \(x_1 = 1\), \(y_1 = 1\), \(x_2 = 2\), \(y_2 = 4\), \(m_1 = 3\), \(m_2 = 2\):\[(x, y) = \left(\frac{2 \cdot 1 + 3 \cdot 2}{3 + 2}, \frac{2 \cdot 1 + 3 \cdot 4}{3 + 2}\right) = \left(\frac{2 + 6}{5}, \frac{2 + 12}{5}\right) = \left(\frac{8}{5}, \frac{14}{5}\right)\]Therefore, the coordinates are \(\left(\frac{8}{5}, \frac{14}{5}\right)\).
02

Substitute the coordinates into the line equation

Substitute the coordinates \(\left(\frac{8}{5}, \frac{14}{5}\right)\) into the line equation \(2x + y = k\):\[2\left(\frac{8}{5}\right) + \frac{14}{5} = k\]Calculate the result:\[\frac{16}{5} + \frac{14}{5} = \frac{16 + 14}{5} = \frac{30}{5} = 6\]So, \(k = 6\).
03

Verify and conclude

The value calculated for \(k\) matches option (c) from the given choices: 6. This verifies our calculations.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Section Formula
The section formula is a useful tool in coordinate geometry when you need to find a specific point along a line joining two known points. It helps in cases of internal division, meaning when the point of interest divides the line segment inside its length.

In our exercise, the section formula was used to determine a point dividing a line segment in a specific ratio. The formula is:
  • For the x-coordinate: \[x = \frac{m_2 \cdot x_1 + m_1 \cdot x_2}{m_1 + m_2}\]
  • For the y-coordinate: \[y = \frac{m_2 \cdot y_1 + m_1 \cdot y_2}{m_1 + m_2}\]
In the formula, \(m_1\) and \(m_2\) are the weights or ratios given for each section of the line joining the points. The formula establishes a system where the coordinates of the dividing point are a weighted average of the coordinates of the given points. This allows precise calculation and understanding of spatial relationships between points.
Line Equation
A line equation in coordinate geometry represents a straight path on a plane. It usually takes the form of \(Ax + By + C = 0\). Alternatively, one might see the line's slope-intercept form: \(y = mx + c\), where \(m\) is the slope and \(c\) is the y-intercept.

In the context of our problem, the line equation provided is \(2x + y = k\). This form is simpler and important for evaluating how points like the one we calculated with the section formula, align along this line. By substituting the coordinates of the point we've established into this line equation, one can solve for \(k\), effectively determining the line's exact position relative to the given points.
Internal Division
Internal division occurs when a point divides a line segment into parts that are both within the endpoints. It's a fundamental concept in coordinate geometry because it helps to find points that lie on the line segment as opposed to outside of it.

The point is determined based on a given ratio, such as the \(3:2\) ratio from our problem, allowing a detailed balance between the segments. Internal division confirms that the splitting point lies within the direct path between two endpoints, such as the points \( (1,1)\) and \( (2,4)\) in our example. By attending to this aspect of division, one can ensure accurate placement of a dividing point within the length of the line itself.
Ratio Division
Ratio division in coordinate geometry explains how a division point relates to each section it divides along a line. Understanding this concept is critical when working with the section formula to calculate specific points.

For instance, the \(3:2\) ratio in this exercise indicates that the dividing point favors the distribution towards the first segment by 3 parts to 2, offering a precise way to measure distances along a line. By dividing the segment into 5 equal parts and associating weights to them, you establish a clear basis for evaluating the line's properties.
  • The order matters: In a \(3:2\) ratio, the numbers \"3\" and \"2\" define how close the point lies to one of the original endpoints compared to the other.
  • Typically, summation of the weights (\(m_1 + m_2\)) is employed to determine the average positioning.
Engaging with ratio division helps one comprehensively manage line division tasks even in more complex geometric arrangements.

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