[問題] PP 計量x3

[yhubi (yhubill)]

142.    這提句意看不太懂  列式就列不出來 @@
The rate of a certain chemical reaction is directly proportional to the square
of the concentration of chemical A present and inversely proportional to the
concentration of chemical B present.
If the concentration of chemical B is increased by 100 percent,
which of the following is closest to the percent change in the concentration
of chemical A required to keep the reaction rate unchanged?

(A) 100% decrease
(B) 50% decrease
(C) 40% decrease
(D) 40% increase
(E) 50% increase


48.
A certain city with a population of 132,000 is to be divided into 11 voting
districts, and no district is to have a population that is more than 10 percent
greater than the population of any other district.
What is the minimum possible population that the least populated district could
have?

(A) 10,700
(B) 10,800
(C) 10,900
(D) 11,000
(E) 11,100

這堤我這樣解:

132000/11=12000

(12000+x)-(12000-x) <= 10%(12000-x)
最多人之區人數-最少人之區人數 小於等於罪少人之區人數的10%

算出x 之後再算12000-x

還是另有其他算法呢??


7.    這題有爬文看之前的文章  還是看不太懂  ((product是積嗎?? 還是我會錯意))
For every positive even integer n, the function h(n) is defined to be the
product of all the even integers from 2 to n, inclusive.
If p is the smallest prime factor of h(100) + 1, then p is

(A) between 2 and 10
(B) between 10 and 20
(C) between 20 and 30
(D) between 30 and 40
(E) greater than 40




答案

 D D E


感謝分享 計算過程



--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 61.217.110.48
※ 編輯: yhubi           來自: 61.217.110.48        (04/01 20:42)
※ 編輯: yhubi           來自: 61.217.110.48        (04/01 20:42)
推 cmchen40:反應速率與A濃度的平方成正比，與B濃度的一次方成反比
推 cmchen40:反應速率~{[A]^2}/[B] 當[B]增加100% 則[A]需增加(√2-1)
→ cmchen40:所以 [A]大約需要增加40%
→ cmchen40:前提是固定是反應速率~忘記打這個條件 @@...
→ yhubi:原來是正比反比  列式也了解了  感謝
推 fly12404:第三題: 基本上2n+1不可能為2的倍數
→ fly12404:3n+1不可能為三的倍數
→ fly12404:題目為2x4x6x8...x98x100 也可以寫成2的五十次方乘以
→ fly12404:(1x2x3x4...x50) <----用之前的想法 即可得知最小質數因
→ fly12404:子大於40  <--答案E
→ yhubi:了解了 原來是用這個觀念 很少遇到這種題目  感謝回答
→ yhubi:也可以說最小質因數大於47囉 47*[(2^50)*(1*2*.沒47..50)]+1