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Ex.15.1 Q3 Introduction to Graphs Solutions - NCERT Maths Class 8

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Question

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?

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

(c) How much did Plant \(A\) grow during the \(3^\rm{rd}\) week?

(d) How much did Plant \(B\) grow from the end of the \(2^\rm{nd}\) week to the end of the \(3^\rm{rd}\) 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.

 Video Solution
Introduction To Graphs
Ex 15.1 | Question 3

Text Solution

Reasoning:

Horizontal axis represents ‘Weeks’ and vertical represents ‘Height’ in \(\rm{cm.}\)

We can find the value of ‘Height’ on vertical axis according to the given value of ‘Weeks’ on the horizontal axis value or vice versa.

Steps:

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

(i) After \(2\) weeks, the height of plant \(A\) was \(7 \;\rm{cm.}\)

(ii) After \(3\) weeks, the height of plant A was \(9 \;\rm{cm.}\)

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

(i) After \(2\) weeks, the height of plant \(B\) was \(7 \;\rm{cm.}\)

(ii) After \(3\) weeks, the height of plant \(B\) was \(10 \;\rm{cm.}\)

(c) Growth of plant \(A\) during \(3\)rd week \(= 9\;\rm{cm} − 7\;\rm{cm} = 2\;\rm{cm}\)

(d) Growth of plant \(B\) from the end of the \(2^\rm{nd}\) week to the end of the \(3 ^\rm{rd}\) week

\(= 10\, \rm{cm} − 7 \, \rm{cm} = 3 \, \rm{cm}\)

(e) Growth of plant \(A\) during \(1^\rm{st}\) week \(= 2\,\rm{cm } − 0 \,\rm{cm } = 2 \,\rm{cm }\)

Growth of plant \(A\) during \(2^\rm{nd}\)week \(= 7 \,\rm{cm} − 2 \,\rm{cm} = 5 \,\rm{cm}\)

Growth of plant A during \(3^\rm{rd}\) week \(= 9\,\rm{cm} − 7 \,\rm{cm} = 2 \,\rm{cm}\)

Therefore, plant \(A\) grew the most, i.e. \(5 \,\rm{cm,}\) during the \(2^\rm{nd}\) week.

(f) Growth of plant \(B\) during \(1^\rm{st}\) week \(= 1\,\rm{cm} − 0 \,\rm{cm} = 1 \,\rm{cm}\)

Growth of plant \(B\) during \(2^\rm{nd}\) week \(= 7\,\rm{cm} − 1\,\rm{cm} = 6 \,\rm{cm}\)

Growth of plant \(B\) during \(3^\rm{rd}\) week \(= 10 \,\rm{cm} − 7\,\rm{cm} = 3\,\rm{cm}\)

Therefore, plant \(B\) grew the least, i.e. \(1 \;\rm{cm,}\) during the \(1^\rm{st}\) week.

(g) At the end of the \(2^\rm{nd}\) week, the heights of both plants were same .i.e. \(7 \rm{cm}\).

  
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