Multiple choice

The age of a man is twice the square of the age of his son. Eight years hence, the age of the man will be 4 years more than three times the age of his son. Find the son's present ages

  1. 5

  2. 3

  3. 6

  4. 4
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let the son's present age be x years. Then the man's present age is 2x². Eight years hence: man's age = 2x² + 8, son's age = x + 8. The condition gives 2x² + 8 = 3(x + 8) + 4 = 3x + 28. Solving 2x² - 3x - 20 = 0 gives x = 4 or x = -2.5. Age cannot be negative, so x = 4.

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