X is directly proportional to the square of Y. What is the percentage change in X, if Y increase by 20%

Mathematics

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Step-by-step solution

4 steps

Let's solve this problem step-by-step.

  1. Write the proportionality relationship.

    If X is directly proportional to the square of Y, we can write:
    X = kY²
    where k is the constant of proportionality.

  2. Define the original and new values of Y.

    Let the original value of Y be Y₁.
    Y₁ = Y
    Y increases by 20%, so the new value of Y, Y₂, is:
    Y₂ = Y₁ + 0.20Y₁
    Y₂ = 1.20Y₁

  3. Calculate the original and new values of X.

    Original X, X₁:
    X₁ = kY₁²

    New X, X₂:
    Substitute Y₂ into the proportionality equation:
    X₂ = k(Y₂)²
    X₂ = k(1.20Y₁)²
    X₂ = k(1.44Y₁²)
    X₂ = 1.44(kY₁²)
    Since X₁ = kY₁², we can write:
    X₂ = 1.44X₁

  4. Calculate the percentage change in X.

    The formula for percentage change is:
    Percentage Change = ((New Value - Original Value) / Original Value) × 100%
    Percentage Change in X = ((X₂ - X₁) / X₁) × 100%
    Substitute X₂ = 1.44X₁:
    Percentage Change in X = ((1.44X₁ - X₁) / X₁) × 100%
    Percentage Change in X = (0.44X₁ / X₁) × 100%
    Percentage Change in X = 0.44 × 100%
    Percentage Change in X = 44%

    The percentage change in X is an increase of 44%.

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