Area by ordinates — Simpson’s 1/3 rule for a curvilinear boundary divided into an even number of equal-width strips states that the area equals: Identify the correct coefficient pattern for extreme, odd, and even offsets.

Difficulty: Easy

Correct Answer: One-third the strip width * [sum of extreme offsets + 4*(sum of remaining odd) + 2*(sum of even)]

Explanation:


Introduction / Context:
When a boundary is irregular, its area can be estimated from offset ordinates at equal intervals using numerical integration rules. Simpson’s 1/3 rule gives a higher-accuracy estimate than the trapezoidal rule by weighting odd and even ordinates differently. This is a standard technique in surveying computations of areas from field measurements.


Given Data / Assumptions:

  • Offsets (ordinates) are taken at equal spacing (strip width = d).
  • The number of strips is even (number of ordinates is odd).
  • Offsets are ordered from the first extreme to the last extreme.


Concept / Approach:
Simpson’s 1/3 rule formula for area A uses weighting 1 for the two extreme offsets, 4 for odd-numbered interior offsets, and 2 for even-numbered interior offsets. The multiplier outside is d/3. This produces improved accuracy for smooth curves by approximating the boundary with parabolic segments over pairs of strips.


Step-by-Step Solution:

Let d be strip width; O0 and On be extreme offsets.Let the interior offsets be O1, O2, O3, ..., On−1.Compute A = (d/3) * [O0 + On + 4*(O1 + O3 + O5 + ...) + 2*(O2 + O4 + O6 + ...)].Ensure the number of strips is even to apply the rule directly.


Verification / Alternative check:
Cross-verify by splitting into parabolic pairs and confirming the 1:4:2 pattern across each pair, then summing for the whole boundary.


Why Other Options Are Wrong:

  • Options (a), (b), and (d) use incorrect coefficients and/or multipliers; they do not match the 1:4:2 with d/3 rule.
  • (e) is wrong because (c) is exactly the Simpson’s 1/3 rule.


Common Pitfalls:
Applying Simpson’s rule with an odd number of strips or confusing which offsets are “odd” vs “even” (count interior positions from the first extreme).


Final Answer:
One-third the strip width * [sum of extreme offsets + 4*(sum of remaining odd) + 2*(sum of even)]

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