A man is 37 years old and his child age is 8. How many years ago was the product of their ages 96

1 answer

Let the number of years ago be denoted as \( x \).

At that time, the man's age would have been \( 37 - x \) and the child's age would have been \( 8 - x \).

The product of their ages at that time is given by the equation:

\[ (37 - x)(8 - x) = 96 \]

Expanding this equation, we have:

\[ 296 - 37x - 8x + x^2 = 96 \]

Combining the terms gives:

\[ x^2 - 45x + 296 - 96 = 0 \]

This simplifies to:

\[ x^2 - 45x + 200 = 0 \]

Now, we can solve this quadratic equation using the quadratic formula:

\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]

Here, \( a = 1 \), \( b = -45 \), and \( c = 200 \).

Calculating the discriminant:

\[ b^2 - 4ac = (-45)^2 - 4 \cdot 1 \cdot 200 = 2025 - 800 = 1225 \]

Taking the square root of the discriminant:

\[ \sqrt{1225} = 35 \]

Now substituting back into the quadratic formula:

\[ x = \frac{45 \pm 35}{2} \]

Calculating the two possible values for \( x \):

  1. \( x = \frac{45 + 35}{2} = \frac{80}{2} = 40 \)
  2. \( x = \frac{45 - 35}{2} = \frac{10}{2} = 5 \)

Since \( x \) represents the number of years ago, we need to consider positive values that fit within the context of their ages.

Thus, the possible solutions are:

  • 40 years ago (not applicable as both ages would not be positive)
  • 5 years ago

Now we check if the product of their ages 5 years ago would indeed equal 96:

The man's age 5 years ago was:

\[ 37 - 5 = 32 \]

The child's age 5 years ago was:

\[ 8 - 5 = 3 \]

Calculating the product:

\[ 32 \times 3 = 96 \]

Indeed, the product equals 96.

Thus, the answer is:

\[ \boxed{5} \]