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Reading of Graphs

In the earlier sections, we have learnt to plot a table of values. By using the table of values we were
able to obtain the graph. Now, in this section, we use the graph to find the solution of the given problems.
Example 14: 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 result are shown by the
adjoining graph. Observe the graph and answer
the following questions.
(a) How much tall was plant A after
2 weeks and 3 weeks?
(b) How much tall was plant B after
2 weeks and 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.

Solution: (a) After 2 weeks plant A was 7 cm high while after 3 weeks it was 9 cm tall.
(b) After 2 weeks plant B was 7 cm high while after 3 weeks it was 10 cm tall.
(c) During 3rd week, plant A grew (9 – 7) cm = 2 cm.

(d) Plant B grew by (10 – 7) cm = 3 cm from the end of 2nd week to the end of 3rd week.
(e) During 2nd week, plant A grew the most, i.e., (7 – 2) cm = 5 cm.
(f) During 1st week, plant B grew the least, i.e., (1 – 0) cm = 1 cm.

(g) At the end of 2nd week both the plants were of
same height.

Example 15: 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
given graph.

(a) What is the scale taken for the time axis?
(b) How much time did the person spend in travelling?

(c) How far is the place of the merchant from the
town?

(d) Did the courier person stop on his way? Explain.

(e) During which period did he ride fastest?

327 Introduction to Graphs