d and C seems to have a linear relationship.
We can test it by calculating the slope at different points:
[tex]m=\frac{\Delta C}{\Delta d}=\frac{9.42-6.28}{3-2}=\frac{3.14}{1}=3.14[/tex]
If we calculate the slope on other 2 points, we get:
[tex]m=\frac{\Delta C}{\Delta d}=\frac{31.4-15.7}{10-5}=\frac{15.7}{5}=3.14[/tex]
We have a constant slope, of value m=3.14.
We can test if this is also a proportional relationship by calculating C/d and veryfing it is a constant for all points:
[tex]\frac{6.28}{2}=\frac{9.42}{3}=\frac{15.7}{5}=\frac{31.4}{10}=3.14[/tex]
The quotient C/d is constant, so there is a proportional relationship.
We can write:
[tex]\frac{C}{d}=3.14[/tex]
and convert that into:
[tex]C=3.14\cdot d[/tex]
Answer: C=3.14*d
