Difficulty: Medium
Correct Answer: (4, 5)
Explanation:
Introduction / Context:
This coordinate-geometry problem tests the section formula (internal division). When a point divides a line segment joining two points in a given ratio internally, its coordinates are a weighted average of the endpoints. The key is to interpret the ratio correctly and apply the formula separately to the x-coordinate and y-coordinate. Because the given point C contains a fraction (7/2), careful arithmetic is required to avoid errors. These questions are common in aptitude exams because they check both conceptual understanding (how ratios work on a segment) and accuracy with fractions.
Given Data / Assumptions:
Concept / Approach:
Internal section formula:
If A divides B(x1, y1) and C(x2, y2) in ratio m:n internally (BA:AC = m:n), then
Ax = (m*x2 + n*x1) / (m + n)
Ay = (m*y2 + n*y1) / (m + n)
Here m = 4 and n = 1, so A is closer to C because the weight on C is larger.
Step-by-Step Solution:
1) Identify m = 4, n = 1, B(6, 1), C(7/2, 6).
2) Compute x-coordinate:
Ax = (4*(7/2) + 1*6) / 5
Ax = (14 + 6) / 5 = 20/5 = 4
3) Compute y-coordinate:
Ay = (4*6 + 1*1) / 5
Ay = (24 + 1) / 5 = 25/5 = 5
4) Therefore A = (4, 5).
Verification / Alternative check:
Since BA:AC = 4:1, A should lie closer to C than to B. C has y = 6 and B has y = 1, so A having y = 5 is closer to 6, which matches the ratio intuition. Also, substituting into the weighted-average formula confirms the exact result without approximation.
Why Other Options Are Wrong:
• (4, 3) and (3, 5): come from mixing up x and y calculations or using the wrong weights.
• (5, 4): often results from reversing B and C in the formula.
• (2, 5): indicates an arithmetic mistake while handling 7/2.
Common Pitfalls:
• Reversing the ratio (using 1:4 instead of 4:1).
• Forgetting that the larger weight applies to the opposite endpoint in the numerator (m multiplies C when ratio is BA:AC = m:n).
• Errors while simplifying 4*(7/2).
Final Answer:
(4, 5)
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