(example)what would you use to measure a school bus?

Whenever we talk about direct or inverse  proportionality  we talk about two variables

Suppose we have two variables x and y  they are said to be in direct proportionality if they one vary same as the other

For eg:

x=3y

Here, whenever x increases y will increase and when x decreases y will decrease.

On the contrary, the two variables when have opposite behaviour

For eg:

x=3/y

Here, whenever x increases y will decrease and when x decreases y will increase.