The variables a and b vary directly, and b=8 when a=2. What is the direct variation equation that relates a and b?

A.

b=2a.

B.

b-4a

C

b=8a

D

b=16a

b= 4a

( This is the correct answer, which is supposed to be option b, but a negative sign was put instead of an equal sign, so you can change appropriately)  

Step-by-step explanation:

Given that a and b vary directly, can be expressed as

a ∝ b

Introducing the constant of proportionality, k, we have that

a = kb

so when a= 2, b= 8 and the constant becomes

2 = k8

k = 2/8=1/ 4

a= 1/4b

Such that

b=4a