又有几道 PS 题，请大家指教

yoo_hoo

1. A rectangular tabletop consists of a piece of laminated wood bordered by a thin metal strip along its four edges. The surface area of the tabletop is x square feet, and the total length of the strip before it was attached was x feet. If the tabletop is 3 feet wide, what is its approximate length, in feet ?

(A) 12        (B) 10         (C) 9         (D) 8          (E) 6          答案是E，请问这题到底是什么意思啊，我一直没有看懂。

2. For all real numbers v, the operation v* is defined by the equation v* = v - v/3.  

If (v*)* = 8, then v =

(A) 15         (B) 18          (C) 21            (D) 24            (E) 27     答案是B，这题该怎么求啊？

3.  In a certain sequence, the first term is 1, and each successive term is 1 more than the reciprocal of the term that immediately precedes it. What is the fifth term of the sequence?

(A) 3 / 5        (B) 5 / 8        (C) 8 / 5        (D) 5 / 3            (E) 9 / 2       答案是C， 这题说是第一个数是1, 后面的每一个的倒数要比前一个大1, 那么first是1, second就是（1/2）+ 1, third是(1/3)+1,  fouth是(1/4)+1, 那么fifth 不就是(1/5)+1 = 6/5 ,我怎么求不出答案C 的呢？

4. What is the least number of digits (including repetitions) needed to express 10¹⁰⁰ in decimal  notation?

(A) 4         (B) 100         (C) 101        (D) 1,000        (E) 1,001       答案是C， 请问the least number of digits (including repetitions) needed to express 10¹⁰⁰ in decimal  notation是什么意思啊， 之后该怎么做呢？

5. A group of 12 people plan to rent a van and agree to share equally the total cost of the rental, which is E dollars. If n of the people decide not to participate at the last minute, by how many dollars will each remaining person's share of the total cost increase?

(A) E / 12-n         (B) 12-n / E         (C) E / 12(12-n)         (D) nE / 12(12-n)

   

(E) (12-n)E / 12n           答案是D，请问这句话 share equally the total cost of the rental, which is E dollars. 是指12个人平摊总额E， 还是指12个人每个人平摊E？如果是前者的话,不就应该是E / 12-n吗，怎么会是D呢，如果是后者，那又该如何求解呢？

谢谢大家，本人不胜感激。   

   

   

   

  

  

  

   

  

   

  

kid

1.这题就是说这个长方形的边长和面积都是x，所以设lenth为L，那么2(L+3)=3L，好像x都没用。解方程得到答案。不理解ets怎么可以把这么简单的题目表述成这个样子。狂倒

2.层层带进去求，因为题目告诉了v*=v-v/3=(2/3)v，所以(v*)*=(2/3)v*=(2/3)[(2/3)v]=8  ->v=18

3. 这5个分别是1,1+1/1=2,1+1/2=3/2,1+2/3=5/3,1+3/5=8/5

4. 10^100写成10进制（英文decimal natation），就是100000000000....000，一共100个0，1个1，所以加起来就是101个数字咯～

5. A group of 12 people plan to rent a van and agree to share equally the total cost of the rental, which is E dollars. If nof the people decide not to participate at the last minute, by how manydollars will each remaining person's share of the total cost increase?
(A) E / 12-n         (B) 12-n /E         (C) E /12(12-n)         (D) nE /12(12-n) （E) (12-n)E /12n          答案是D，请问这句话 share equally the total cost of the rental, which is E dollars. 是指12个人平摊总额E， 还是指12个人每个人平摊E？如果是前者的话,不就应该是E / 12-n吗，怎么会是D呢，如果是后者，那又该如何求解呢？

这位兄弟一看就是sc不过关，哈哈～which就近修饰啊，当然是指总数呀！～，所以列式就是：
E/（12-n）-E/n，通分就得到答案了～