Problem 43
Question
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) \(\frac{11}{5}\)
Step-by-Step Solution
Verified Answer
The value of \(k\) is 6.
1Step 1: 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 \(\left(\frac{8}{5}, \frac{14}{5}\right)\).
2Step 2: 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, \(k = 6\).
3Step 3: Verify and conclude
The value calculated for \(k\) matches option (c) from the given choices: 6. This verifies our calculations.
Key Concepts
Section FormulaLine EquationInternal DivisionRatio Division
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:
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: \[y = \frac{m_2 \cdot y_1 + m_1 \cdot y_2}{m_1 + m_2}\]
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.
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.
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.
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.
Other exercises in this chapter
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