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Q.Without actually performing the long division, state whether the following rational numbers will have a terminating decimal expansion or a non-terminating repeating decimal expansion:

(i) ${}^{13}/{}_{3125}$

(ii) ${}^{17}/{}_{8}$

(iii) ${}^{64}/{}_{455}$

(iv) ${}^{15}/{}_{1600}$  

(v) ${}^{29}/{}_{343}$

 (vi)$23/{{2}^{3}}{{5}^{2}}$  

(vii) ${}^{129}/{}_{{{2}^{2}}{{5}^{7}}{{7}^{5}}}$

(viii) ${}^{6}/{}_{15}$

(ix) ${}^{35}/{}_{50}$

(x) ${}^{77}/{}_{210}$

Note: If the denominator has only factors of 2 and 5 or in the form of ${{2}^{m}}\times {{5}^{n}}$  then it has terminating decimal expansion.

If the denominator has factors other than 2 and 5 then we can say that it has a non-terminating decimal expansion.

(i) ${}^{13}/{}_{3125}$

Factorizing the denominator, we get,

$3125=5\times 5\times 5\times 5\times 5={{5}^{5}}$

Since, the denominator has only 5 as its factor, ${}^{13}/{}_{3125}$ has a terminating decimal expansion.

(ii)${}^{17}/{}_{8}$

Factorizing the denominator, we get,

$8=2\times 2\times 2$

Since, the denominator has only 2 as its factor, ${}^{17}/{}_{8}$ has a terminating decimal expansion.

(iii) ${}^{64}/{}_{455}$

Factorizing the denominator, we get,

$455=5\times 7\times 13$

Since, the denominator is not in the form of  ${{2}^{m}}\times {{5}^{n}}$ ,thus ${}^{64}/{}_{455}$ has a non-terminating decimal expansion.

(iv)${}^{15}/{}_{1600}$  

Factorizing the denominator, we get,

$1600={{2}^{6}}\times {{5}^{2}}$

Since, the denominator is in the form of ${{2}^{m}}\times {{5}^{n}}$ , thus  ${}^{15}/{}_{1600}$  has a terminating decimal expansion.

(v)${}^{29}/{}_{343}$

Factorizing the denominator, we get,

$343=7\times 7\times 7$

Since, the denominator is not in the form of ${{2}^{m}}\times {{5}^{n}}$ thus ${}^{29}/{}_{343}$ has a non-terminating decimal expansion.

(vi)${}^{23}/{}_{{{2}^{3}}{{5}^{2}}}$

Clearly, the denominator is in the form of ${{2}^{m}}\times {{5}^{n}}$

Hence, ${}^{23}/{}_{{{2}^{3}}{{5}^{2}}}$ has a terminating decimal expansion.

(vii) ${}^{129}/{}_{{{2}^{2}}{{5}^{7}}{{7}^{5}}}$

As you can see, the denominator is not in the form of ${{2}^{m}}\times {{5}^{n}}$

Hence, ${}^{129}/{}_{{{2}^{2}}{{5}^{7}}{{7}^{5}}}$has a non-terminating decimal expansion.

(viii) ${}^{6}/{}_{15}$

${}^{6}/{}_{15}={}^{2}/{}_{5}$

Since, the denominator has only 5 as its factor,

 thus,  ${}^{6}/{}_{15}$ has a terminating decimal expansion.

(ix) ${}^{35}/{}_{50}$

${}^{35}/{}_{50}={}^{7}/{}_{10}$

 Factorising the denominator, we get,

$10=2\times 5$

The denominator is in the form of ${{2}^{m}}\times {{5}^{n}}$ where m and n are non negative integers

Hence, ${}^{35}/{}_{50}$ has a terminating decimal expansion.

(x) ${}^{77}/{}_{210}$

${}^{77}/{}_{210}$=${}^{7\times 11}/{}_{7\times 30}$ $={}^{11}/{}_{30}$

Factorising the denominator, we get,

$30=2\times 3\times 5$

The denominator is not in the form of ${{2}^{m}}\times {{5}^{n}}$ .where m and n are non negative integers.

Hence, ${}^{77}/{}_{210}$ has a non-terminating repeating decimal expansion.