Answer: The constant of variation value of 7.
Step-by-step explanation: We are given cost of 0.8 meter of a silk ribbon = $5.60.
Let us assume y be the total cost for x meter of a silk ribbon and k is the constant of variation.
So, we can set up an equation for proportion relationship:
y = k x.
Let us plug x=0.8 and y= 5.60, in above proportion relationship equation, we get
5.60 = k (0.8).
Dividing both sides by 0.8, we get
5.60/0.8 = k(0.8)/0.8
k =7.
Therefore, the constant of variation value of 7.