NCERT Solutions for Class 8 Maths Chapter 15 Introduction to Graphs

Ans : (a) At 1 p.m., the patient's temperature was 38.5° C. 
(b) The patient's temperature was 38.5° C at 12 noon. 
(c) The patient's temperature was same at 1 p.m. and 2 p.m. 
(d) The graph between the times 1 p.m. and 2 p.m. is parallel to the x-axis. The temperature at 1 p.m. and 2 p.m. is 36.5° C. So, the temperature at 1:30 p.m. is 36.5° C 
(e) During the following periods, the patient's temperature showed an upward trend. 9 a.m. to 10 a.m., 10 a.m. to 11 a.m., 2 p.m. to 3 p.m. 

Ans : (a) (i) 2002, the sales were Rs 4 crores. 
(ii) In 2006, the sales were Rs 8 crores. 
(b) (i) In 2003, the sales were Rs 7 crores. 
(ii) In 2005 the sales were Rs 10 crores. 
(c) (i) In 2002 the sales were Rs 4 crores and in 2006, the sales were Rs 8 crores. 
Difference between the sales in 2002 and 2006 = Rs (8 -4) crores =Rs 4 crores 
(d) Difference between the sales of the year 2006 and 2005 = Rs (10-8) crores =Rs 2 crores 
Difference between the sales of the year 2005 and 2004= Rs (10 - 6) crores = Rs 4 crores 
Difference between the sales of the year 2004 and 2003= Rs (7-6) crore = Rs 1 crore 
Difference between the sales of the year 2003 and 2002 =Rs (7 -4) crores =Rs 3 crores 
Hence, the difference was the maximum in the year 2005 as compared to its previous year 

Ans : (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 cm -7 cm = 2 cm 
(d) Growth of plant B from the end of the 2nd week to the end of the 3rd week = 10 cm -7 cm =3 cm 
(e) Growth of plant A during 1st week = 2 cm -0 cm = 2 cm 
Growth of plant A during 2nd week = 7 cm - 2 cm = 5 cm 
Growth of plant A during 3d week =9 cm -7 cm= 2 cm 
Therefore, plant A grew the most, i.e. 5 cm, during the 2nd week. 
(f) Growth Of plant B during ISt week = 1 cm -0 cm =1 cm 
Growth of plant 3 during 2nd week = 7 cm -1 cm = 6 cm 
Growth Of plant 3 during 38 week = 10 cm -7 cm = 3 cm 
Therefore, plant B grew the least, i.e. 1 cm, during the 1st week. 
(g) At the end of the 2nd week, the heights of both plants were same. 

Ans : (a) The forecast temperature was same as the actual temperature on Tuesday, 
Friday, and Sunday. 
(b) The maximum forecast temperature during the week was 35° C. 
(c) The minimum actual temperature during the week was 35° C. 
(d) The actual temperature differs the most from the forecast temperature on Thursday. 

Ans : (a) By taking the years on x-axis and the number of days on y-axis and taking scale 
as 1 unit = 2 days on y-axis and 2 unit = 1 year on x axis, the linear graph of the 
given information can be drawn as follows. 



(b) dy taking the years on x-axis and population on y-axis and scale as 1 unit 0.5 thousand on y-axis and 2 unit = 1 year on x-axis, the linear graph of the given information can be drawn as follows.