CBSEGrade 11MathematicsStraight Lines

Line Segment Midpoint Dilemma?

Point M is the midpoint of line segment AB. D is a point on AB such that AD:DB = 3:4. Prove that MB = 2MC.

💬 1 answers0 votes👁 1 views04 July 2026

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📌 CONCEPT: To prove that MB = 2MC, we need to use the concept of mid-point and section formula in the context of line segments.

📐 RULE / FORMULA: According to the section formula, if a point P(x, y) divides a line segment joining the points A(x1, y1) and B(x2, y2) in the ratio m:n, then the coordinates of P are given by ((mx2 + nx1)/(m+n), (my2 + ny1)/(m+n)). We will use this formula to find the coordinates of M and C.

💡 WORKED EXAMPLE: Let A be (1, 3) and B be (7, 9). Since M is the midpoint of AB, we can find its coordinates using the midpoint formula. Let D divide AB in the ratio 3:4. We can use the section formula to find the coordinates of D. Then, we can find the coordinates of C by taking M as the midpoint of MD. Finally, we can calculate MB and MC to verify that MB = 2MC.

⚠️ COMMON MISTAKE: Students often get confused between the midpoint and section formula, which leads to incorrect calculations. They should carefully apply the correct formula and verify their calculations to avoid this mistake.

04 Jul 26

📖 Chapter Resource

Straight Lines

Mathematics · Grade 11

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