If 7, 12, 21 and x are in proportion, the value of x is:
2026
If 7, 12, 21 and x are in proportion, the value of x is:
Answer: A. 36 — ConceptA proportion states that two ratios are equal: a/b = c/d. In such a proportion, the product of the extremes equals the product of the means: ad = bc.…
- A.
36
- B.
27
- C.
24
- D.
35
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Correct answer: A
Concept
A proportion states that two ratios are equal: a/b = c/d.
In such a proportion, the product of the extremes equals the product of the means: ad = bc.
Application
Write the given proportion as 7/12 = 21/x.
Cross-multiply: 7x = 12 × 21.
Divide both sides by 7: x = (12 × 21)/7 = 12 × 3 = 36.
Cross-check
Substitution gives 7/12 = 21/36; both ratios simplify to 7/12.
Therefore, x = 36.
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