Final answer:
To find the value of x when y is 2.0 given y is directly proportional to x, calculate the constant of proportionality with the given values and apply it to the new y value to obtain x, which is 4.0.
Step-by-step explanation:
When dealing with a situation where y is directly proportional to x, we use the formula y = kx, where k is the constant of proportionality. Given that x=7.2 when y=3.6, we can find the constant of proportionality (k) by rearranging the formula to k = y/x, and then substituting the given values: k = 3.6/7.2 = 0.5. Now that we have the value of k, we can find the value of x when y=2.0 using the formula x = y/k. Substituting the values, we get x = 2.0/0.5 = 4.0.