# Lesson 5: Linear Relations. Distance-Time Graphs

In this lesson you will learn about linear relations and what they mean. One of the most common examples of a linear relation is the relationship between distance and time when a distance changes over time at a constant rate.

A linear relation is represented by a straight-line – a relationship between a variable and a constant. Linear relations can be expressed in 4 different ways: a graph, a table of values, a word description and an equation.

In this lesson we will compare two objects moving and discuss the relationship between distance, time and speed while comparing the graphs representing the motion patterns of the two objects.

You will learn why the equation D = vt (or D = st) is a direct proportion and how knowing the time and speed one can determine the distance traveled.