Final answer:
When two variables are directly proportional, changes in one variable result in proportional changes in the other variable. This relationship can be represented by an equation and shown graphically as a straight line passing through the origin.
Step-by-step explanation:
When the quotient of two variables is equal to a constant, each variable is said to be directly proportional with the other. In other words, if one variable increases or decreases, the other variable will also increase or decrease in the same proportion.
For example, if the constant is 2 and the variables are x and y, we can write the equation as y = 2x. This means that if x doubles, y will also double. Similarly, if x is halved, y will be halved as well.
Direct proportionality can be represented graphically as a straight line passing through the origin (0,0) on a coordinate plane.