A statement of Assertion \((A)\) is followed by a statement of Reason \((R)\). 
 
Choose the correct option
 
Assertion \((A)\): If \(3:4 :: 9:12\), then \(3 \times 12 = 4 \times 9\).
 
Reason \((R)\): In a proportion, the ratio of first to second equals the ratio of third to fourth.