## Applications of Linear graphs

 Credit: Pixabay.com

A linear graph shows the variation between two quantities. One quantity is plotted on x-axis & other quantity is plotted on y-axis.

↪ The quantity whose value depend on the other is called dependent variable.

↪ The quantity which affects the value of dependent variable is called Independent variable (or sometimes control variable).

↪ Generally, independent quantity is plotted on x-axis and dependent quantity is plotted on y-axis.

↪ When two quantities are in direct variation, the graph will always be linear.

## Quantity and Cost

Cost of any item depends on its quantity. Therefore between quantity & cost, quantity is independent variable whereas cost is dependent variable.

Example: Draw graph for the following data.

↪ Scale : 2 unit = 1 on horizontal axis; 2 unit = ₹ 5 on vertical axis.

↪ Mark Numbers along horizontal axis.

↪ Mark Cost along vertical axis.

↪ Plot the points : (1,5), (2, 10), (3, 15), (4,20), (5,25).

↪ Join the points. We get a graph that is a line.

 Graph of Quantity Vs Cost

## Principal and Simple Interest (SI)

SI depends on the Principal borrowed. More the Principal more will be the SI at constant rate of interest. Therefore between Principal & SI, Principal is independent variable whereas SI is dependent variable.

Example: Draw graph for the following data.

↪Scale : 2 unit = ₹ 1000 on horizontal axis; 2 unit = ₹ 80 on vertical axis.

↪ Mark Deposits along horizontal axis.

↪ Mark Simple Interest along vertical axis.

↪ Plot the points : (1000,80), (2000, 160), (3000, 240), (4000,320) etc.

↪ Join the points. We get a linear graph.

 Graph of Principal Vs Simple Interest

## Time and Distance

At constant speed, distance traveled is directly proportional to the time taken. Therefore between time & distance, time is independent variable whereas distance is dependent variable.

Example: Draw graph for the following data.

↪ Scale: Horizontal: 2 units = 1 hour, Vertical: 2 unit = 40 km

↪ Mark time on horizontal axis.

↪ Mark distance on vertical axis.

↪ Plot the points: (6, 40), (7, 80), (8, 120), (9, 160), (10,200).

↪ Join the points. We get a linear graph.

 Distance-Time Graph
 Coordinate Geometry ⏩