NCERT - Mathematics

Book: NCERT - Mathematics

Chapter: 15. Introduction to Graphs

Subject: Maths - Class 8th

Q. No. 3 of Exercises 15.1

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3

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


A. How high was Plant A after (i) 2 weeks (ii) 3 weeks?


B. How high was Plant B after (i) 2 weeks (ii) 3 weeks?


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


D. How much did Plant B grow from the end of the 2nd week to the end of the3rd week?


E. During which week did Plant A grow most?


F. During which week did Plant B grow least?


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

A.


i. After 2 weeks, the height of plant A was 7 cm.


ii. After 3 weeks, the height of plant A was 9 cm.


B.


i. After 2 weeks, the height of plant B was 7 cm.


ii. After 3 weeks, the height of plant B was 10 cm.


C. Growth of plant A during 3rd week


= 9 -7


= 2 cm


D. Growth of plant B from the end of 2nd week to the end of 3rd week:


= 10 -7


= 3 cm


E. Growth of plant A during 1st week:


= 2-0


= 2cm


Growth of plant A during 2nd week:


= 7 -2


= 5 cm


Growth of plant A during 3rd week:


= 9 -7


= 2 cm


Hence, A grew the most in its 2nd week i.e. 5 cm.


F. Growth of plant B during 1st week:


= 1 -0


= 1 cm


Growth of plant B during 2nd week:


= 7 -1


= 6 cm


Growth of plant B during 3rd week:


= 10 -7


= 3 cm


Hence, plant B grew the least in 1st week i.e. 1cm


G. The heights of both the plants were same at the end of 2nd week.


3

Chapter Exercises

Exercises 15.1
Exercises 15.2
Exercises 15.3

More Exercise Questions

1

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

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


B. When was the patient’s temperature 38.5° C?



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


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


E. During which periods did the patients’ temperature showed an upward trend?
2

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

A. What were the sales in (i) 2002 (ii) 2006?


B. What were the sales in (i) 2003 (ii) 2005?


C. Compute the difference between the sales in 2002 and 2006.


D. In which year was there the greatest difference between the sales as comparedto its previous year?
3

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


A. How high was Plant A after (i) 2 weeks (ii) 3 weeks?


B. How high was Plant B after (i) 2 weeks (ii) 3 weeks?


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


D. How much did Plant B grow from the end of the 2nd week to the end of the3rd week?


E. During which week did Plant A grow most?


F. During which week did Plant B grow least?


G. Were the two plants of the same height during any week shown here? Specify.
4

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

A. On which days was the forecast temperature the same as the actual temperature?


B. What was the maximum forecast temperature during the week?


C. What was the minimum actual temperature during the week?


D. On which day did the actual temperature differ the most from the forecasttemperature?
5

Use the tables below to draw linear graphs.

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


Year



2003



2004



2005



2006



Days



8



10



5



12



B. 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
6

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

A. What is the scale taken for the time axis?


B. How much time did the person take for the travel?


C. How far is the place of the merchant from the town?


D. Did the person stop on his way? Explain.


E. During which period did he ride fastest?
7

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

(i)


(ii)


(iii)


(iv)