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Tamil Nadu Board of Secondary EducationSSLC (English Medium) Class 9

Express the following decimal expression into rational number -21.2137¯ - Mathematics

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Question

Express the following decimal expression into rational number

`-21.213bar(7)`

Sum

Solution

Let x = −21.2137777… ………..(1)

10x = −212.137777…… ………..(2)

100x = −2121.37777…… …………(3)

1000x = −21213.77777…. ………..(4)

10000x = 212137.77777….. …………(5)

(Now period of decimal is 1, multiply equation (4) it by 10)

(5) – (4)

10000x – 1000x = (−212137.7777…) – (−21213.7777…)

9000x = −190924

x = `-190924/9000`

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Period of Decimal
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Chapter 2: Real Numbers - Exercise 2.2 [Page 52]

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Samacheer Kalvi Mathematics [English] Class 9 TN Board
Chapter 2 Real Numbers
Exercise 2.2 | Q 4. (vi) | Page 52
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