<em>The constant of proportionality is the ratio between two directly proportional quantities. In our tomato example, that ratio is $3.00/2, which equals $1.50. Two quantities are directly proportional when they increase and decrease at the same rate.</em>
This question is asking you to find the circumference of the circle. To do this the equation is C=D where C is circumference and D is diameter. So, C= 3.14* 2.5 which equals 7.85 ft.