

InterviewSolution
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Express the following decimal expression into rational numbers.(i) \(0.\overline{24}\)(ii) \(2.\overline{327}\)(iii) -5.132(iv) \(3.1\bar{7}\)(v) \(17.\overline{215}\)(vi) \(-21.213\bar{7}\) |
Answer» (i) \(0.\overline{24}\) Let x = \(0.\overline{24}\) = 0.24242424 … (1) (Here period of decimal is 2, multiply equation (1) by 100) 100x = 24.242424 … (2) (2) – (1) 100x – x = 24.242424… – 0.242424… 99x = 24 x = \(\frac{24}{99}\) (ii) \(2.\overline{327}\) Let x = 2.327327327… (1) (Here period of decimal is 3, multiply equation (1) by 1000) 1000x = 2327.327… (2) (2) – (1) 1000x – x = 2327.327327… – 2.327327… 999x = 2325 x = \(\frac{2325}{999}\) (iii) -5.132 x = -5.132 = \(\frac{-5132}{1000}=\frac{-1283}{250}\) (iv) \(3.1\bar{7}\) Let x = 3.1777 … (1) (Here the repeating decimal digit is 7, which is the second digit after the decimal point, multiply equation (1) by 10) 10x = 31.7777 … (2) (Now period of decimal is 1, multiply equation (2) by 10) 100x = 317.7777… (3) (3) – (2) 100x – 10x = 317.777… – 31.777… 90x = 286 x = \(\frac{286}{90}=\frac{143}{45}\) (v) \(17.\overline{215}\) Let x = 17.215215 … (1) 1000x = 17215.215215 … (2) (2) – (1) 1000x – x = 17215.215215… – 17.215… 999x = 17198 x = \(\frac{17198}{999}\) (vi) \(-21.213\bar{7}\) 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 = \(-\frac{190924}{9000}\) |
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