I'm studying algebra and I came across a problem that involves direct proportions. The problem states that a quantity 'y' is directly proportional to 'x' squared. If y equals 64 when x equals 4, I need to find the value of y when x equals 6. Can you find a similar problem on this Q&A forum and provide the solution?

1 answer

Certainly! The relationship described in your problem indicates that \( y \) is directly proportional to \( x^2 \). This can be expressed mathematically as:

\[ y = kx^2 \]

where \( k \) is the constant of proportionality. From the information given, we know that when \( x = 4 \), \( y = 64 \). We can use this information to find \( k \).

  1. Substitute \( x \) and \( y \) into the equation:

\[ 64 = k(4^2) \]

  1. Calculate \( 4^2 \):

\[ 64 = k(16) \]

  1. Solve for \( k \):

\[ k = \frac{64}{16} = 4 \]

Now that we have the value of \( k \), we can write the equation as:

\[ y = 4x^2 \]

Next, we need to find \( y \) when \( x = 6 \):

  1. Substitute \( x = 6 \) into the equation:

\[ y = 4(6^2) \]

  1. Calculate \( 6^2 \):

\[ y = 4(36) \]

  1. Finally, calculate \( y \):

\[ y = 144 \]

Thus, when \( x = 6 \), the value of \( y \) is 144.

In summary:

  • \( k = 4 \)
  • When \( x = 6 \), \( y = 144 \).