Proportional Relationship
Two variables x and y are in a proportional relationship if:
y = k x
Where k is the constant of proportionality.
The value of k can be determined by knowing one point of the function.
A)
Ann's car can travel y = 228 miles on x = 6 gallons of gas. The proportion between the miles traveled and the gallons of gas can be written as:
y = k x
Substituting:
228 = k (6)
Solving for k:
k = 228 / 6
k = 38
Now our function is:
y = 38x
B) If we know x = 7 gallons, we can calculate:
y = 38*7
y = 266
Ann drove 266 miles
