[原创] Ans of jjQ (10^-2-10^-3?)

Hello! - I am pretty sure about the answer of these Qs.  (of course correct me if I m wrong.) Took me a while to figure it out. I hope this will help others who are taking test in this coming few days. My test is tomorrow! ADD oil together ba~

152、x是closed to 10^-2 more than10^-3?

1)x更接近10^-4 而不是10^-1

2)x更接近10^-4而不是10^-2

 ANS: E (wrong! it should be B)

The midpoint between 10^-2 and 10^-3 should be (0.01+0.001)/2=0.0055.  So we need to determine if x < 0.0055 or x > 0.0055. 

Statement (1): The midpoint between 10^-4 and 10^-1 is (0.0001+0.1)/2 = 0.05005.  Since x is closer to 10^-4, x < 0.05005.  With x < 0.05005, x can still be < 0.0055 or > 0.0055.  So statement 1 alone is not sufficient.

Statement (2): The midpoint between 10^-4 and 10^-2 is (0.0001+0.01)/2 = 0.00505.  Since x is closer to 10^-4, x < 0.00505.  Since x < 0.00505, x is also < 0.0055.  So Statement 2 alone is sufficient, and the answer should be B.

152、x 是個正數。問x 距離10E-2和距離10E-3哪個近。
(1)x距離10E-2比距離10E-1近
(2) x距離10E-3比距離10E-1近

答：A (Wrong! It should be A)

Midpoint between 10^-2 and 10^-3 = (0.01+0.001)/2 = 0.0055.  Need to know if x < 0.0055 or x > 0.0055.

Statement (1): midpoint between 10^-2 and 10^-1 = (0.1+0.01)/2 = 0.055.  Since x is closer to 10^-2, x < 0.055.  With x < 0.055, x can still be < 0.0055 or > 0.0055.  So Statement 1 alone is not sufficient.

Statement (2): midpoint between 10^-3 and 10^-1 = (0.1+0.001)/2 = 0.0505.  Since x is closer to 10^-3, x < 0.0505.  With x < 0.0505, x can still be < 0.0055 or > 0.0055.  So Statement 2 alone is not sufficient.

Combining Statements (1) and (2), x < 0.055 and x < 0.0505 give you x < 0.0505.  x can still be < 0.0055 or > 0.0055, so together they are not sufficient.  The answer should be E.

Midpoint between 10^-2 and 10^-3 = (0.01+0.001)/2 = 0.0055.  Need to know if x < 0.0055 or x > 0.0055.

Statement (1): midpoint between 10^-2 and 10^-1 = (0.1+0.01)/2 = 0.055.  Since x is closer to 10^-2, x < 0.055.  With x < 0.055, x can still be < 0.0055 or > 0.0055.  So Statement 1 alone is not sufficient.

Statement (2): midpoint between 10^-3 and 10^-1 = (0.1+0.001)/2 = 0.0505.  Since x is closer to 10^-3, x < 0.0505.  With x < 0.0505, x can still be < 0.0055 or > 0.0055.  So Statement 2 alone is not sufficient.

Combining Statements (1) and (2), x < 0.055 and x < 0.0505 give you x < 0.0505.  x can still be < 0.0055 or > 0.0055, so together they are not sufficient.  The answer should be E.

Midpoint between 10^-2 and 10^-3 = (0.01+0.001)/2 = 0.0055.  Need to know if x < 0.0055 or x > 0.0055.

Statement (1): midpoint between 10^-2 and 10^-1 = (0.1+0.01)/2 = 0.055.  Since x is closer to 10^-2, x < 0.055.  With x < 0.055, x can still be < 0.0055 or > 0.0055.  So Statement 1 alone is not sufficient.

Statement (2): midpoint between 10^-3 and 10^-1 = (0.1+0.001)/2 = 0.0505.  Since x is closer to 10^-3, x < 0.0505.  With x < 0.0505, x can still be < 0.0055 or > 0.0055.  So Statement 2 alone is not sufficient.

Combining Statements (1) and (2), x < 0.055 and x < 0.0505 give you x < 0.0505.  x can still be < 0.0055 or > 0.0055, so together they are not sufficient.  The answer should be E.

Midpoint between 10^-2 and 10^-3 = (0.01+0.001)/2 = 0.0055.  Need to know if x < 0.0055 or x > 0.0055.

Statement (1): midpoint between 10^-2 and 10^-1 = (0.1+0.01)/2 = 0.055.  Since x is closer to 10^-2, x < 0.055.  With x < 0.055, x can still be < 0.0055 or > 0.0055.  So Statement 1 alone is not sufficient.

Statement (2): midpoint between 10^-3 and 10^-1 = (0.1+0.001)/2 = 0.0505.  Since x is closer to 10^-3, x < 0.0505.  With x < 0.0505, x can still be < 0.0055 or > 0.0055.  So Statement 2 alone is not sufficient.

Combining Statements (1) and (2), x < 0.055 and x < 0.0505 give you x < 0.0505.  x can still be < 0.0055 or > 0.0055, so together they are not sufficient.  The answer should be E.

FeiFei27、問數字A離10^(-2)近還是離10^(-3)近？(參考)

(1)A離10^(-1)比離10^(-4)近

(2)A離10^(-2)比離10^(-4)近

【答案】A

【思路】

現在我們假設數字A離10^(-2)比離10^(-3)近，則|A-10^(-2)|<|A-10^(-3)|

通過圖形和計算化解的A>[10^(-2)+10^(-3)]/2

同理可得：

（1）|A-10^(-1)|<|A-10^(-4)| A>[10^(-1)+10^(-4)]/2

（2）|A-10^(-2)|<|A-10^(-4)| A>[10^(-2)+10^(-4)]/2

則只有條件一是符合的，因為[10^(-1)+10^(-4)]/2>[10^(-2)+10^(-3)]/2 說明假設是成立的。

For Q27: again need to know if A < 0.0055 or A > 0.0055.

Statement (1): midpoint between 10^-1 and 10^-4 = (0.1+0.0001)/2 = 0.05005.  Since A is closer to 10^-1, A > 0.05005.  Since A > 0.05005, A is also > 0.0055.  So A is closer to 10^-2 than 10^-3.  Statement 1 alone is sufficient. 

Statement (2): midpoint between 10^-2 and 10^-4 = (0.01+0.0001)/2 = 0.00505.  Since A is closer to 10^-2, A > 0.00505.  When A > 0.00505, A can be < 0.0055 or A can be > 0.0055.  So Statement 2 alone is not sufficient.  The answer is A.

同意同意!

我也觉得应该这样解!

说一家商店按照wholesales为60的成本买了东西。然后按照原来retail的价格打40% discount售出。如果wholesale的利润25%， 问按照retail原价，利润是多少

这题就是wholesale, retail绕来绕去. 

60/（1-25%）/（1-40%）得retail 原价 然后用 [60/（1-25%）-60]/retail 原价，得利润%

楼主这题有什么高见么