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Introduction to Graphs : Exercise 15.3 (Mathematics NCERT Class 8th)


Q.1 Draw the graphs for the following tables of values, with suitable scales on the axes.
(a) Cost of apples

Number of apples

1

2

3

4

5

Cost (in Rs) 5 10 15 20

25

(b) Distance travelled by a car

Time (in hours)

6 a.m.

7 a.m.

8 a.m.

9 a.m.

Distance (in km) 40 80 120

160

(i) How much distance did the car cover during the period 7.30 a.m. to 8 a.m?
(ii) What was the time when the car had covered a distance of 100 km since it’s start?

(c) Interest on deposits for a year.

Deposit (in Rs)

1000

2000

3000

4000

5000

Simple Intereset (in Rs) 80 160 240 320

400

(i) Does the graph pass through the origin?
(ii) Use the graph to find the interest on Rs 2500 for a year.
(iii) To get an interest of Rs 280 per year, how much money should be deposited?
Sol. (a) The graph for given data is as shown below:
Here, x-axis represents the number of apples and scale taken is 1 unit = 1 apple, whereas y-axis represents cost (in Rs) and scale taken is 1 unit = Rs 5.(b) The graph for given data is as shown below:
Here, x-axis represents the time and scale taken is 2 units = 1 hour, whereas y-axis represents distance (in km) and scale taken is 2 units = 40 km.(i) The car covered distance of 20 km during the period 7.30 a.m. to 8 a.m.
(ii) The time was 7.30 am when the car had covered a distance of 100 km since it’s start.

(c) The graph for given data is as shown below:
Here, x-axis represents the deposit (in Rs) and scale taken is 1 unit = Rs 1000, whereas y-axis represents simple interest (in Rs) and scale taken is 1 unit = Rs 80.(i) Yes, the graph do passes through the origin.
(ii) From the graph, it can be seen that the interest on Rs 2500 for a year is Rs 200.
(iii) Rs 3500 should be deposited to get an interest of Rs 280 per year.

Q.2 Draw a graph for the following.
(i)

Side of square (in cm)

2

3

3.5

5

6

Perimeter (in cm) 8 12 14 20

24

Is it a linear graph?
(ii)

Side of square (in cm)

2

3

4

5

6

Area (in cm2) 4 9 16 25

36

Is it a linear graph?
Sol. (i) The graph for given data is as shown below:
Here, x-axis represents the side of square (in cm) and scale taken is 1 unit = 1 cm, whereas y-axis represents perimeter (in cm) and scale taken is 1 unit = 4 cm.Yes, it is a linear graph.
(ii) The graph for given data is as shown below:
Here, x-axis represents the side of square (in cm) and scale taken is 1 unit = 1 cm, whereas y-axis represents area (in cm2) and scale taken is 1 unit = 4 cm2.No, it is not a linear graph.



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