Question

Suppose y varies directly as x², and y = 160 when x = 4. Find y when x = 6.

Answer 1

Finding the constant of proportionality :

• y = kx²
• 160 = k(4)²
• k = 10

Finding y when x = 6 :

• y = 10(6)²
• y = 10(36)
• y = 360

The value of y is 360 when x = 6.