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NCERT solutions Mathematics Class 8 chapter 15 Introduction to Graphs

Chapters

NCERT Mathematics Class 8

Mathematics Textbook for Class 8

Chapter 15 - Introduction to Graphs

Pages 236 - 239

The following graph shows the temperature of a patient in a hospital, recorded every hour.

1) What was the patient’s temperature at 1 p.m.?

2) When was the patient’s temperature 38.5°C?

3) The patient’s temperature was the same two times during the period given. What were these two times?

4) What was the temperature at 1.30 p.m.? How did you arrive at your answer?

5) During which periods did the patients’ temperature showed an upward trend?

Q 1 | Page 236

The following line graph shows the yearly sales figures for a manufacturing company.

1) What were the sales in (a) 2002 (b) 2006?

2) What were the sales in (a) 2003 (b) 2005?

3) Compute the difference between the sales in 2002 and 2006.

4) In which year was there the greatest difference between the sales as compared
to its previous year?

Q 2 | Page 237

For an experiment in Botany, two different plants, plant A and plant B were grown under similar laboratory conditions. Their heights were measured at the end of each week for 3 weeks. The results are shown by the following graph.

1) How high was Plant A after (a) 2 weeks (b) 3weeks?

2) How high was Plant B after (a) 2 weeks (b) 3weeks?

3) How much did Plant A grow during the 3rd week?

4) How much did Plant B grow from the end of the 2nd week to the end of the 3rd week?

5) During which week did Plant A grow most?

6) During which week did Plant B grow least?

7) Were the two plants of the same height during any week shown here? Specify.

Q 3 | Page 237

The following graph shows the temperature forecast and the actual temperature for each day of a week.

1) On which days was the forecast temperature the same as the actual temperature?

2) What was the maximum forecast temperature during the week?

3) What was the minimum actual temperature during the week?

4) On which day did the actual temperature differ the most from the forecast temperature?

Q 4 | Page 238

Use the tables below to draw linear graphs

The number of days a hill side city received snow in different years.

Year 2003 2004 2005 2006
Days 8 10 5 12 
Q 5.1 | Page 238

Use the tables below to draw linear graphs.

Population (in thousands) of men and women in a village in different years.

Year 2003 2004 2005 2006 2007
Number of men 12 12.5 13 13.2 13.5
Number of women 11.3 11.9 13 13.6 12.8 
Q 5.2 | Page 238

A courier-person cycles from a town to a neighboring suburban area to deliver a parcel to a merchant. His distance from the town at different times is shown by the following graph.

1) What is the scale taken for the time axis?

2) How much time did the person take for the travel?

3) How far is the place of the merchant from the town?

4) Did the person stop on his way? Explain.

5) During which period did he ride fastest?

Q 6 | Page 239

Can there be a time temperature graph as follows? Justify you’re answer:

Q 7.1 | Page 239

Can there be a time-temperature graph as follows? Justify your answer

Q 7.2 | Page 239

Can there be a time-temperature graph as follows? Justify your answer

Q 7.3 | Page 239

Can there be a time temperature graph as follows? Justify you’re answer:

Q 7.4 | Page 239

Page 243

Plot the following points on a graph sheet. Verify if they lie on a line

A(4, 0), B(4, 2), C(4, 6), D(4, 2.5)

Q 1.1 | Page 243

Plot the following points on a graph sheet. Verify if they lie on a line

P(1, 1), Q(2, 2), R(3, 3), S(4, 4)

Q 1.2 | Page 243

Plot the following points on a graph sheet. Verify if they lie on a line

K(2, 3), L(5, 3), M(5, 5), N(2, 5)

Q 1.3 | Page 243

Draw the line passing through (2, 3) and (3, 2). Find the coordinates of the points at which this line meets the x-axis and y-axis.

Q 2 | Page 243

Write the coordinates of the vertices of each of these adjoining figures.

Q 3 | Page 243

State whether True or False. Correct those are false.

A point whose x coordinate is zero and y-coordinate is non-zero will lie on the y-axis.

Q 4.1 | Page 243

State whether True or False. Correct those are false.

A point whose y coordinate is zero and x-coordinate is 5 will lie on y-axis.

Q 4.2 | Page 243

State whether True or False. Correct those are false.

The coordinates of the origin are (0, 0).

Q 4.3 | Page 243

Pages 247 - 248

Draw the graphs for the following tables of values, with suitable scales on the axes.

Cost of apples

Number of apples 1 2 3 4 5
Cost (in Rs) 5 10 15 20 25
Q 1.1 | Page 247

Draw the graphs for the following tables of values, with suitable scales on the axes.

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 

1)  How much distance did the car cover during the period 7.30 a.m. to 8 a.m.?

2) What was the time when the car had covered a distance of 100 km since its start?

Q 1.2 | Page 247

Draw the graphs for the following tables of values, with suitable scales on the axes. 

Interest on deposits for a year:

Deposit (in Rs) 1000 2000 3000 4000 5000
Simple interest (in Rs) 80 160 240 320 400

1) Does the graph pass through the origin?

2) Use the graph to find the interest on Rs 2500 for a year:

3) To get an interest of Rs 280 per year, how much money should be deposited?

Q 1.3 | Page 247

Draw a graph for the following.

Side of square (in cm) 2 3 3.5 5 5
Perimeter (in cm) 8 12 14 20 24

Is it a linear graph?

 

Q 2.1 | Page 248

Draw a graph for the following.

Side of square (in cm) 2 3 4 5 6
Area (in cm2) 4 9 16 25 36

Is it a linear graph?

 

Q 2.2 | Page 248

NCERT Mathematics Class 8

Mathematics Textbook for Class 8
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