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Componendo operation on a:b = c:d gives:
A(a-b):b = (c-d):d
B(a+b):b = (c+d):d
Ca:c = b:d
Db:a = d:c
Answer & Solution
Correct answer: B. (a+b):b = (c+d):d
1. Per OCR: "If a:b=c:d which implies a+b:b=c+d:d then we say that the operation of Componendo is performed."
2. Add denominator to numerator on each side.
3. Distinct from Dividendo (subtract).
_Source: ICMAI BoS CMA Foundation Paper 3 (FBMS) — Paper3_07042026.pdf, Module 1 §1.1 (page 13)_