## NCERT Solutions for Class 8 Chapter 15 Introduction to Graphs -Free PDF Download

Free PDF download of NCERT Solutions Maths Class 8 Solutions Chapter 15 â€“ Introduction to Graphs solved by Expert Maths Teachers on CoolGyan.Org. All Chapter 15 â€“ Introduction to Graphs Questions with Solutions for NCERT to help you to revise complete Syllabus and Score More marks.

Maths Revision Notes for Class 8

Chapter Name |
Introduction to Graphs |

Chapter |
Chapter 15 |

Exercise |
Exercise 15.1 |

Class |
Class 8 |

Subject |
Maths NCERT Solutions |

Board |
CBSE |

TEXTBOOK |
CBSE NCERT |

Category |
NCERT Solutions |

**NCERT SOLVED**

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

**(a) What was the patientâ€™s temperature at 1 p.m.?**

**(b) When was the patientâ€™s temperature 38.5Â° C?**

**(c) The patientâ€™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 patientsâ€™ temperature showed an upward trend?**

**Ans.**Â **(a)**Â The patientâ€™s temperature was 36.5^{o}Â C at 1 p.m.

**(b)**Â The patientâ€™s temperature was 38.5^{o}Â C at 12 noon.

**(c)**Â The patientâ€™s temperature was same at 1 p.m. and 2 p.m.

**(d)**Â The temperature at 1.30 p.m. is 36.5^{o}Â C. The point between 1 p.m. and 2 p.m.,Â axis is equidistant from the two points showing 1 p.m. and 2 p.m. So, it represents 01.30 p.m. Similarly, the point onÂ axis, between 36^{o}Â C and 37^{o}Â C will represent 36.5^{o}Â C.

**(e)**Â The patientâ€™s temperature showed an upward trend from 9 a.m. to 11 a.m., 11 a. m. to 12 noon and 2 p.m. to 3 p.m.

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

**(a)**Â **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 compared to its previous year?**

**Ans.**Â

**(a)**Â The sales in:Â

**(i)**Â 2002 was Rs.4 crores andÂ

**(ii)**Â 2006 was Rs.8 crores.

**(b)**Â The sales in:Â

**(i)**Â 2003 was Rs.7 croresÂ

**(ii)**Â 2005 was Rs.10 crores.

**(c)**Â The difference of sales in 2002 and 2006 = Rs.8 crores â€“ Rs.4 crores = Rs.4 crores

**(d)**Â In the year 2005, there was the greatest difference between the sales as compared to its previous year, which is (Rs.10 crores â€“ Rs.6 crores) = Rs.4 crores.

**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 each week for 3 weeks. The results are shown by the following graph.**

**(a)**Â **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 the 3rd 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.**

**Ans.**Â **(a)**Â **(i)**Â The plant A was 7 cm high after 2 weeks and

**(ii)**Â after 3 weeks it was 9 cm high.

**(b) (i)**Â Plant B was also 7 cm high after 2 weeks and

**(ii)**Â after 3 weeks it was 10 cm high.

**(c)**Â Plant A grew = 9 cm â€“ 7 cm = 2 cm during 3^{rd}Â week.

**(d)**Â Plant B grew during end of the 2^{nd}Â week to the end of the 3^{rd}Â week

= 10 cm â€“ 7 cm = 3 cm.

**(e)**Â Plant A grew the highest during second week.

**(f)**Â Plant B grew the least during first week.

**(g)**Â At the end of the second week, plant A and B were of the same height.

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

**(a)Â**

**On which days was the forecast temperature the same as the actual temperature?**

**(b)Â**

**What was the maximum forecast temperature during the week?**

**(c)Â**

**What was the minimum actual temperature during the week?**

**(d) On which day did the actual temperature differ the most from the forecast**

temperature?

temperature?

**Ans.(a)**Â On Tuesday, Friday and Sunday, the forecast temperature was same as the actual temperature.

**(b)**Â The maximum forecast temperature was 35

^{o}Â C.

**(c)**Â The minimum actual temperature was 15

^{o}Â C.

**(d)**Â The actual temperature differed the most from the forecast temperature on Thursday.

**5. Use the tables below to draw linear graphs.**

**(a)**Â **The number of days a hill side city received snow in different years.**

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

**Ans.**Â Â **(a)**

**(b)**

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

**Ans.**Â **(a)**Â 4 units = 1 hour.

**(b)**Â The person tookÂ Â hours for the travel.

**(c)**Â It was 22 km far from the town.

**(d)**Â Yes, this has been indicated by the horizontal part of the graph. He stayed from 10 am to 10.30 am.

**(e)**Â He rode the fastest between 8 am and 9 am.

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

**Ans.**Â Â **(i)**Â Â Â It is showing the increase in temperature.

**(ii)**Â Â It is showing the decrease in temperature.

**(iii)**Â The graph figureÂ **(iii)**Â is not possible since temperature is increasing very rapidly which is not possible.

**(iv)**Â It is showing constant temperature.