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Mathematics

Express each of following as a vulgar fraction in simplest form :

(i) 0.50.\overline{5}

(ii) 0.430.\overline{43}

(iii) 0.1580.\overline{158}

(iv) 1.31.\overline{3}

(v) 4.174.\overline{17}

(vi) 0.120.\overline{12}

(vii) 0.1360.1\overline{36}

(viii) 1.571.5\overline{7}

Rational Irrational Nos

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Answer

(i) 0.50.\overline{5}

Let x = 0.50.\overline{5}.

⇒ x = 0.555..     ………..(1)

⇒ 10x = 5.555..     ……….(2)

On subtracting (1) from (2), we get :

⇒ 10x - x = 5.555… - 0.555…

⇒ 9x = 5

⇒ x = 59\dfrac{5}{9}

Hence, 0.5=590.\overline{5} = \dfrac{5}{9}.

(ii) 0.430.\overline{43}

Let x = 0.430.\overline{43}.

⇒ x = 0.434343..     ………(1)

⇒ 100x = 43.4343..     ……..(2)

On subtracting (1) from (2), we get :

⇒ 100x - x = 43.4343…. - 0.4343……

⇒ 99x = 43

⇒ x = 4399\dfrac{43}{99}

Hence, 0.43=43990.\overline{43} = \dfrac{43}{99}.

(iii) 0.1580.\overline{158}

Let x = 0.1580.\overline{158}

⇒ x = 0.158158..     ……(1)

⇒ 1000x = 158.158158..     ……(2)

On subtracting (1) from (2), we get :

⇒ 1000x - x = 158.158158…. - 0.158158…..

⇒ 999x = 158

⇒ x = 158999\dfrac{158}{999}

Hence, 0.158=1589990.\overline{158} = \dfrac{158}{999}.

(iv) 1.31.\overline{3}

Let x = 1.31.\overline{3}

⇒ x = 1.3333..     ……(1)

⇒ 10x = 13.333..     ……(2)

On subtracting (1) from (2), we get :

⇒ 10x - x = 13.333.. - 1.333..

⇒ 9x = 12

⇒ x = 129\dfrac{12}{9}

⇒ x = 43\dfrac{4}{3}

Hence, 1.3=431.\overline{3} = \dfrac{4}{3}.

(v) 4.174.\overline{17}

Let x = 4.174.\overline{17}

⇒ x = 4.1717..     ……..(1)

⇒ 100x = 417.1717..     …….(2)

On subtracting (1) from (2), we get :

⇒ 100x - x = 417.1717….. - 4.1717…..

⇒ 99x = 413

⇒ x = 41399\dfrac{413}{99}

Hence, 4.17=413994.\overline{17} = \dfrac{413}{99}.

(vi) 0.120.\overline{12}

Let x = 0.120.\overline{12}

⇒ x = 0.1222..     ………..(1)

⇒ 100x = 12.222…(ii)

On subtracting (i) from (ii), we get

⇒ 99x = 12

⇒ x = 1299\dfrac{12}{99}

⇒ x = 12÷399÷3\dfrac{12÷3}{99÷3}

⇒ x = 433\dfrac{4}{33}

Hence, 0.12… = 433\dfrac{4}{33}.

(vii) 0.1360.1\overline{36}

Let x = 0.1360.1\overline{36}

⇒ x = 0.13636..     ………..(1)

⇒ 10x = 1.3636..     ………..(2)

⇒ 1000x = 136.3636..     ………..(3)

On subtracting (2) from (3), we get

⇒ 1000x - 10x = 136.3636.. - 1.3636..

⇒ 990x = 135

⇒ x = 135990\dfrac{135}{990}

⇒ x = 135÷45990÷45\dfrac{135 ÷ 45}{990 ÷ 45}

⇒ x = 322\dfrac{3}{22}

Hence, 0.1363220.1\overline{36}\dfrac{3}{22}.

(viii) 1.571.5\overline{7}

Let x = 1.571.5\overline{7}.

⇒ x = 1.5777..     ………..(1)

⇒ 10x = 15.777..     ………..(2)

⇒ 100x = 157.7777..     ………..(3)

On subtracting (i) from (iii), we get

⇒ 100x - 10x = 157.7777.. - 15.777……

⇒ 90x = 142

⇒ x = 14290\dfrac{142}{90}

⇒ x = 142÷290÷2\dfrac{142 ÷ 2}{90 ÷ 2}

⇒ x = 7145\dfrac{71}{45}

Hence, 1.57=71451.5\overline{7} = \dfrac{71}{45}.

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