Question

Please help me solve this thanks

Answer 1

Answer:

A

Step-by-step explanation:

let r represent rate and d distance.

Given that r varies directly as d² then the equation relating them is

r = kd² ← k is the constant of variation

To find k use the condition r = 4 when d = 15, then

4 = k × 15² = 225k ( divide both sides by 225 )

k = $\frac{4}{225}$

r = $\frac{4}{225}$ d²  ← equation of variation

When r = 9, then

9 = $\frac{4}{225}$d² ( multiply both sides by 225 )

2025 = 4d² ( divide both sides by 4 )

506.25 = d² ( take the square root of both sides )

d = $\sqrt{506.25}$ = 22.5 = 22 $\frac{1}{2}$ → A