Chapter 3
The World of Numbers
CBSE Class 9
Mathematics Solutions
Educart Mathematics class Class 9 NCERT Exemplar cover
Question:

Try to extend this method for constructing line segments of lengths 3\sqrt{3} and 5\sqrt{5} using a ruler and a compass. Generalise this method to construct a line segment of any length of the form n\sqrt{n}, where nn is a positive integer. [Page No. 56]

Answer: Verified

Represent 3\sqrt{3} on Number Line:

Let's draw the number line

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Answer image

Represent 5\sqrt{5} on Number Line: Let's draw the number line

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Hence, point PP is 5\sqrt{5}.

Generalising: to get n\sqrt{n}, make a right triangle with legs n1\sqrt{n-1} and 1, because (n1)2+12=n\sqrt{(n-1)^2} + 1^2 = n. Repeating the 'add a unit perpendicular' step from a length-1 start produces 2,3,4,5,\sqrt{2}, \sqrt{3}, \sqrt{4}, \sqrt{5}, \dots in turn each new hypotenuse is n\sqrt{n} (one more than the last). A compass then transfers any of these to the number line.

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