Difficulty: Easy
Correct Answer: four pairs of points, four acute angle crossings and two obtuse angle crossings
Explanation:
Introduction / Context:A scissors crossover allows simultaneous crossing and switching between two parallel tracks within a compact footprint. It combines two interlaced crossovers with a diamond crossing, resulting in a sophisticated assembly of points and crossings that must be correctly counted for design and maintenance purposes.
Given Data / Assumptions:
Concept / Approach:
Each crossover requires two pairs of points (right-hand and left-hand), so a scissors crossover includes four pairs of points in total. The diamond contributes two obtuse crossings, and the interlaced layout completes a total of four acute crossings. This is the standard count widely referenced in permanent way practice.
Step-by-Step Solution:
Two crossovers → 4 pairs of points (each crossover has 2 pairs).Central diamond → 2 obtuse crossings.Overall acute crossings in the combined layout → 4.Hence: 4 pairs of points, 4 acute, 2 obtuse crossings.Verification / Alternative check (if short method exists):
Refer to a standard scissors crossover diagram and count the elements; tally matches the chosen option.
Why Other Options Are Wrong:
Options claiming six acute or four obtuse crossings inflate the crossing count and do not reflect the canonical layout of a scissors crossover.
Common Pitfalls (misconceptions, mistakes):
Confusing a simple crossover plus separate diamond with a true interlaced scissors; miscounting acute vs obtuse crossings in the central diamond.
Final Answer:
four pairs of points, four acute angle crossings and two obtuse angle crossings
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