求教两道数学题

蓝兰紫籽

If J, S, and V are points on the number line, what is the distance between S and V?   E
(1)   The distance between J and S is 20.
(2)   The distance between J and V is 25.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

The rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical A present and is inversely proportinal to the concentation of chemical B. If the concentration of chemcal B is increased by 100%, which of the following is closest to the percentage change in the concentation of chemical A required to keep the reaction rate unchanged? E
A 100% decrease  
B 50%decreased  
C 40%decreased  
D 50%increased  
E 40%increased

第一题个人觉得是选C，第二题知道肯定是DE中的一个，但是40%是怎么算出来的呀？？
文科大四党表示数学离我真的太遥远了啊啊啊啊啊~~

treewing929

第一條是 e, 要仔細一點. 題目沒有說次序!
jsv 還是 sjv?!

treewing929

其實第二條不用算, 問題要 KEEP UNCHANGED

現在 b 上升 100%, 那麼 Rate 下降100%,
要 offset, 最好當然是上升100% 去保持不變.
上升40%^2較上升50%^2 好. 因為後者上升太多了.