Class 8 Maths

# Introduction to Graphs

## Exercise 15.1

Question 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?

Answer: at 1:00 PM and 2:00 PM

(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?

Answer: from 10:00 to 11:00 AM and from 2:00 to 3:00 PM

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

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

Answer: (i) Rs. 4 crores (ii) Rs. 8 crores

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

Answer: (i) Rs. 7 Crores (ii) Rs. 10 crores

(c) Compute the difference between the sales in 2002 and 2006.

Answer: 8-4=4; Sales of 2006 is Rs. 4 crores more than that of 2002

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

Answer: 2005 sees the greatest jump in sales which clear from the steepest angle between these years.

Question 3: 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.

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

Answer: (i) 7 cm (ii) 9 cm

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

Answer: (i) 7 cm (ii) 10 cm

(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?

Answer: from week 1 to week 2 by 5 cm

(f) During which week did Plant B grow least?

Answer: In the first week by 1 cm

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

Answer: Second week both have a height of 7 cm

Question 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?

Answer: Tuesday 20˚ c, Friday 15˚ c and Sunday 35˚ c

(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?

Answer: Thursday, by 7.5˚ c ( Notice the largest gap between two lines)

Question 5: Use the tables below to draw linear graphs.

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

 Year Days 2003 2004 2005 2006 8 10 5 12

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

 Year No. of men No. of women 2003 2004 2005 2006 2007 12 12.5 13 13.2 13.5 11.3 11.9 13 13.6 12.8

Question 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.

Answer: Between 10:00 AM to 11:00 AM the line is horizontal, which explains that the person took rest between these timings

(e) During which period did he ride fastest?

Answer: Between 8:00 AM and 9:00 AM he traveled 10 kms, (look for the steepest angle made by the line)