搜题请搜索小程序“爱下问搜题”
问题 单项选择题

A decorator bought a bolt of defective cloth that he judged to be

usable, in which ease the cost would be $0.80 per usable yard. If it was later found that only

of the bolt could be used, what was the actual cost per usable yard

答案

参考答案：B

解析： 设这匹布共有a码，每码可以用的布的实际成本为x美元，则根据题意可得：
[*]

填空题

将15.6gNa2O2与2.7gAl粉混合后，投入足量的水中，充分反应（设能产生的气体全部放出）。

（1）Na2O2与水反应的化学方程式为                                            ，

该反应中的转移电子的物质的量为          mol。

（2）反应结束时生成气体的体积在标准状况下为       L。

（3）取agNa2O2与Al粉组成的混合物，放入适量的水中，固体完全溶解，在标准状况下放出气体的体积为VL，则V的取值范围是           ，（用含a的代数式表示，结果可不化简）。
查看答案
单项选择题

Chauncy, an English bulldog, received 1,618 votes in the Mr. Bulldog USA competition, giving him approximately 20 percent of the vote. Approximately what percent of the remaining votes would he have needed to receive in order to win 30 percent of the total votes ？（）

A. 10%

B. 12.5%

C. 15%

D. 17.5%

E. 20%
查看答案