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Application of graph in real life. Graphs are useful in many fields for finding out many variables. Let us see how graph can be used in our lives. Malathi wanted to know in which month she had gone the maximum and minimum number of days to school. She made the following table and plotted
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Graphs are useful in many fields for finding out many variables. Let us see how graph can be used in our lives. Malathi wanted to know in which month she had gone the maximum and minimum number of days to school. She made the following table and plotted a graph to find it. She plotted these points on a graph On the X axis she marked month. On the Y axis she marked the number of working days. She took the scale as, X axis 1 cm = 1 month Y axis 1 cm = 5 days She plotted the points on the graph and joined the points Now she found the answer !
Maximum number of days in July Maximum number of days in December.
Example 1 : Plot a graph for the quantity of oil (in litres) and it’s cost (in rupees). Find also the cost of 33 litres of oil from the graph. Solution: Step 1: On the X axis mark quantity of oil. On the Y axis mark the cost of oil. Step 2: Take suitable scale as, X axis 1 cm = 10 litres Y axis 1 cm = 50 rupees Step 3: Plot the points Step 4: Draw a line joining the points Step 5: To find the cost of 33 litres Draw a vertical line from point 33 on X axis to the line drawn. Draw horizontal line from intersection point on the line to the Y axis It meets at 165 on Y axis. So, the cost of 33 litres oil is 165 rupees 165 33
Example 2 : Joel walks at a speed of 3 kilometers/hour. Draw a time-distance graph of his speed and find the time taken to cover 18 kilometer. Solution: Step 1: Joel walks at a speed of 3 kilometers per hour. It means he walks 3 km in 1 hour , 6 km in 2 hours , ( 2 hours = 2 x 3 =6 km ) 9 km in 3 hours , ( 3 hours = 3 x 3 =9 km ) 12 km in 4 hours , ( 4 hours = 4 x 3 =12 km ) 15 km in 5 hours. ( 5 hours = 5 x 3 =15 km ) Put this in a table, Step 2: On the X axis mark time in hours. On the Y axis mark the distance in km. Step 3: Take suitable scale as, X axis 1 cm = 1 hour Y axis 1 cm = 3 kilometers
Step 3: Plot the points Step 4: Draw a line joining the points Step 5: To Find the time taken to cover 15 km Draw a vertical line from point 6 on X axis to the line drawn. Draw horizontal line from intersection point on the line to the Y axis. It meets at 18 on Y axis. Answer: The time taken to travel 18 km is 5 hours
Try these • Plot a graph for the number of ice creams and it’s cost (in rupees). Find also the • cost of 21 Ice cream from the graph. • A postman rides his bicycle at a speed of 10 kilometers/hour. Draw • a time-distance graph of his speed and find the time taken by him to • cover 55 kilometers.