Re: [計量] 幾題問題請教
: : 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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