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The square of Faizal's age, in years, is 12 more than his father's age. One year ago, Faizal's age was \( \frac{1}{6} \) of his father's age. Find Faizal's present age.

Ask by Jimenez Schwartz. in Singapore
Feb 28,2025

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Answer

Faizal is 7 years old.

Solution

Let Faizal's present age be F years and his father's present age be D years. We are given: 1. Faizal's age squared is 12 more than his father's age:   F² = D + 12 2. One year ago, Faizal's age was 1/6 of his father's age:   F - 1 = (D - 1) / 6 Step 1: Express D in terms of F from the first equation.   F² = D + 12 ⟹ D = F² - 12 Step 2: Substitute D = F² - 12 into the second equation:   F - 1 = (F² - 12 - 1) / 6   F - 1 = (F² - 13) / 6 Step 3: Multiply both sides by 6 to eliminate the fraction:   6(F - 1) = F² - 13   6F - 6 = F² - 13 Step 4: Rearrange the equation to form a quadratic equation:   F² - 6F - 13 + 6 = 0   F² - 6F - 7 = 0 Step 5: Solve the quadratic equation F² - 6F - 7 = 0 using the quadratic formula:   F = [6 ± √(36 + 28)] / 2   F = [6 ± √64] / 2   F = [6 ± 8] / 2 This gives two potential solutions:   F = (6 + 8) / 2 = 14 / 2 = 7   F = (6 - 8) / 2 = (-2) / 2 = -1 Since age cannot be negative, we discard F = -1. Thus, Faizal's present age is 7 years. Verification:   Father's age D = F² - 12 = 7² - 12 = 49 - 12 = 37   One year ago: Faizal's age = 7 - 1 = 6, and father's age = 37 - 1 = 36;   Check: 6 is indeed 1/6 of 36. Answer: Faizal is 7 years old.

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Let's denote Faizal's current age as \( F \) and his father's current age as \( P \). From the problem, we have two equations to work with: 1. The square of Faizal's age is 12 more than his father's age: \[ F^2 = P + 12 \] 2. One year ago, Faizal’s age was \( \frac{1}{6} \) of his father’s age at that time: \[ F - 1 = \frac{1}{6}(P - 1) \] Now, we can manipulate these equations to find Faizal’s current age. From the second equation, we multiply both sides by 6 to eliminate the fraction: \[ 6(F - 1) = P - 1 \] This simplifies to: \[ 6F - 6 = P - 1 \quad \Rightarrow \quad P = 6F - 5 \] Next, we substitute \( P \) in the first equation: \[ F^2 = (6F - 5) + 12 \] This simplifies to: \[ F^2 = 6F + 7 \] Rearranging gives us a quadratic equation: \[ F^2 - 6F - 7 = 0 \] Now we can solve for \( F \) using the quadratic formula: \[ F = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} = \frac{6 \pm \sqrt{(-6)^2 - 4 \cdot 1 \cdot (-7)}}{2 \cdot 1} \] Calculating the discriminant: \[ = \frac{6 \pm \sqrt{36 + 28}}{2} = \frac{6 \pm \sqrt{64}}{2} = \frac{6 \pm 8}{2} \] Now we have two potential solutions for \( F \): 1. \( F = \frac{14}{2} = 7 \) 2. \( F = \frac{-2}{2} = -1 \) (not valid, since age can't be negative) Thus, Faizal's present age is: \[ \boxed{7} \text{ years old.} \]

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