Q142
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% drcrease
(D) 40% increase
(E) 50% increase
Answer : D
Q143
In a survey of students, each student selected from a list of 12 songs the 2 songs that the student liked best. If each song was selected 4 times, how many students were surveyed?
(不是很懂題目的意思)
(A) 96
(B) 48
(C) 32
(D) 24
(E) 18
Answer : D
請教如何算這兩題呢 謝謝