: : 6. Which of the following fractions has a equivalent that is a terminating : : decimal ? : : A. 10/189 B. 15/196 C. 16/225 D. 39/128 : : Ans: D (看不懂題目) : 個位數2 or 5結尾的是terminating decimal(注意需不需要約分) : : 以上六題 懇請解答!! google到比較完整的題目..你的D選項等於以下答案選項的E選項.. 題目應該是問哪個分數換算成小數位會終止..不會進入循環小數 Which of the following fractions has a decimal equivalent that is a terminating decimal? A. 10/189 B. 15/196 C. 16/225 D. 25/144 E. 39 /128 First of all we should look for denominator characteristics. If any denominator is a prime no. except 2 or 5, then it would be a repeating decimal fraction. (主要是用分母的數值進行因式分解來判斷.質數除了2和5.其他皆會造成循環小數) If the denomiantor is a multiple of 3, the result is repeating decimal fraction. (分母為3的倍數時..為循環小數) Here, A, C, D represent repeating decimal fraction. (A,C,D皆為3的倍數..所以是repeating decimal fraction) Here, we can not factorize 196(2*2*2*2*11) in 2^n*5^m fashion but 128=2^7*5^0. (因式分解B和E) So, B represents repeating decimal fraction and E terminating decimal fraction (B選項有個因子為11(非2or5)..會造成循環..所以E應該是正解.. --

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