NCERT solution class 8 chapter 15 Introduction to Graphs

Exercise 15.1   Exercise 15.2   Exercise 15.3

Exercise 15.3

Question 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 its start?

(c) Interest on deposits for a year:

Deposit (in Rs)

1000

2000

3000

4000

5000

Simple interest (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) Taking a suitable scale (for x-axis, 1 unit = 1 apple and for y-axis, 1 unit = Rs 5), we can mark the number of apples on x-axis and the cost of apples on y-axis. A graph of the given data is as follows.


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(b) Taking a suitable scale (for x-axis, 2 units = 1 hour and for y-axis, 2 units = 40 km), we can represent the time on x-axis and the distance covered by the car on y-axis. A graph of the given data is as follows.

(i) During the period 7:30 a.m. to 8 a.m., the car covered a distance of 20 km.

(ii) The car covered a distance of 100 km at 7:30 a.m. since its start.

(c) Taking a suitable scale,

For x-axis, 1 unit = Rs 1000 and for y-axis, 1 unit = Rs 80

We can represent the deposit on x-axis and the interest earned on that deposit on y-axis. A graph of the given data is obtained as follows.

From the graph, the following points can be observed.

(i) Yes. The graph passes through the origin.

(ii) The interest earned in a year on a deposit of Rs 2500 is Rs 200.

(iii) To get an interest of Rs 280 per year, Rs 3500 should be deposited.

 

 

Question 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) Choosing a suitable scale,

For x-axis, 1 unit = 1 cm and for y-axis, 1 unit = 4 cm

We can represent the side of a square on x-axis and the perimeter of that square on y-axis. A graph of the given data is drawn as follows.

It is a linear graph.

(ii)Choosing a suitable scale,

For x-axis, 1 unit = 1 cm and for y-axis, 1 unit = 4 cm2

We can represent the side of a square on the x-axis and the area of that square on y-axis. A graph of the given data is as follows.

It is not a linear graph.

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