If 36 : 81 :: x : 63, then what is the value of x?
Correct Answer: 28
Subject: Mathematics
Explanation: According to the proportion rule: Product of extremes = Product of means.
36 × 63 = 81 × x
⇒ x = (36 × 63) / 81 = (4 × 9 × 7 × 9) / (9 × 9) = 4 × 7 = 28.