Answer:
The equation relates the variables is y = 8x ⇒ D
Step-by-step explanation:
If x and y vary directly (y ∝ x), then y = k x, where
- k is the constant of variation
- k can be found using the initial value of x and y
∵ The variable x and y vary directly
∴ y ∝ x
→ By using the rule above
∴ y = k x
∵ y = 40 when x = 5
∴ The initial values of x and y are x = 5 and y = 40
→ Substitute them in the equation above to find k
∵ 40 = k(5)
∴ 40 = 5k
→ Divide both sides by 5
∵ =
∴ 8 = k
→ Substitute the value of k in the equation above
∴ y = 8x
∴ The equation relates the variables is y = 8x