## 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 – Introduction to Graphs solved by Expert Maths Teachers on CoolGyan.Org. All Chapter 15 – 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 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?**

**Ans.** **(a)** The patient’s temperature was 36.5^{o} C at 1 p.m.

**(b)** The patient’s temperature was 38.5^{o} C at 12 noon.

**(c)** The patient’s temperature was same at 1 p.m. and 2 p.m.

**(d)** The temperature at 1.30 p.m. is 36.5^{o} C. The point between 1 p.m. and 2 p.m., 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 on axis, between 36^{o} C and 37^{o} C will represent 36.5^{o} C.

**(e)** The patient’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)** **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.** **(a)** The sales in: **(i)** 2002 was Rs.4 crores and **(ii)** 2006 was Rs.8 crores.

**(b)** The sales in: **(i)** 2003 was Rs.7 crores **(ii)** 2005 was Rs.10 crores.

**(c)** The difference of sales in 2002 and 2006 = Rs.8 crores – Rs.4 crores = Rs.4 crores

**(d)** In the year 2005, there was the greatest difference between the sales as compared to its previous year, which is (Rs.10 crores – 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)** **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.** **(a)** **(i)** The plant A was 7 cm high after 2 weeks and

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

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

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

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

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

= 10 cm – 7 cm = 3 cm.

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

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

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

**4. ****The following graph shows the temperature forecast and the actual temperature for each 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 forecast temperature?**

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

**(b)** The maximum forecast temperature was 35^{o} C.

**(c)** The minimum actual temperature was 15^{o} C.

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

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

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

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

**Ans.** **(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.** **(a)** 4 units = 1 hour.

**(b)** The person took hours for the travel.

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

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

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

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

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

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

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

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