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Mathematics

You know that 17\dfrac{1}{7} = 0.1428570.\overline{142857}. Can you predict what the decimal expansions of 27\dfrac{2}{7}, 37\dfrac{3}{7}, 47\dfrac{4}{7}, 57\dfrac{5}{7}, 67\dfrac{6}{7} are, without actually doing the long division? If so, how?

[Hint : Study the remainders while finding the value of 17\dfrac{1}{7} carefully.]

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Answer

Given,

17\dfrac{1}{7} = 0.1428570.\overline{142857}

(i) 27\dfrac{2}{7} = 2×172 \times \dfrac{1}{7}

= 2×0.1428572 \times 0.\overline{142857}

= 0.2857140.\overline{285714}

(ii) 37\dfrac{3}{7} = 3×173 \times \dfrac{1}{7}

= 3×0.1428573 \times 0.\overline{142857}

= 0.4285710.\overline{428571}

(iii) 47\dfrac{4}{7} = 4×174 \times \dfrac{1}{7}

= 4×0.1428574 \times 0.\overline{142857}

= 0.5714280.\overline{571428}

(iv) 57\dfrac{5}{7} = 5×175 \times \dfrac{1}{7}

= 5×0.1428575 \times 0.\overline{142857}

= 0.7142850.\overline{714285}

(v)67\dfrac{6}{7} = 6×176 \times \dfrac{1}{7}

= 6×0.1428576 \times 0.\overline{142857}

= 0.8571420.\overline{857142}

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