2026 · Q29
A variable y is directly proportional to a variable quantity xⁿ. Given that when x = 2, y = 20.8 and when x = 3, y = 105.3. Which one of the following is the constant of proportionality if it is greater than 1?
Elementary MathematicsRatio and Proportion
- A1.1
- B1.3
- C2
- D4
Explanation
With y = kxⁿ, dividing the two observations gives (3/2)ⁿ = 105.3/20.8 = 5.0625. Since 1.5⁴ = 5.0625, n = 4. Then k = 20.8/2⁴ = 20.8/16 = 1.3, option B.