Question 25

The speed at which a runner races one mile and the total time it takes demonstrates inverse proportionality.

In this relationship, as the speed of the runner increases, the time taken to complete the mile decreases, illustrating the concept of inverse proportionality.

A) Average resting heart rate and score on an intelligence test

This option does not demonstrate inverse proportionality, as there is no clear relationship where an increase in one variable leads to a decrease in the other. Instead, both variables may be influenced by different factors independently.

B) The speed at which a runner races one mile and the total time it takes

This option correctly illustrates inverse proportionality. When the speed of the runner increases, the time taken to complete the mile decreases, establishing a direct inverse relationship between these two variables.

C) The volume of gasoline pumped at a gas station and the total cost

This relationship is directly proportional. As the volume of gasoline increases, the total cost also increases at a constant rate, showing that both variables move in the same direction rather than inversely.

D) The length of a pipe and the total weight of the pipe

This relationship is also directly proportional. As the length of the pipe increases, the total weight correspondingly increases, indicating that both variables are positively correlated rather than exhibiting inverse proportionality.

Conclusion

The relationship between the speed at which a runner races one mile and the total time taken is the only one that demonstrates inverse proportionality, as an increase in speed results in a decrease in time. All other options either show direct proportionality or lack a clear relationship, making them incorrect in the context of this question.