题干

一只铅笔和一只钢笔一共8.4元,钢笔的单价是铅笔的6倍,钢笔和铅笔的单价各是多少元?
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解:一只钢笔的价钱相当于6只铅笔的价钱,所以1只钢笔=6只铅笔,所以7只铅笔的价钱是8.4元所以单价是: 8.4÷7=1.2(元) 钢笔的单价是: 1.2×6=7.2(元)答:一只钢笔7.2元,一只铅笔1.2元.

同类题3

阅读理解

    Why do Americans struggle with watching their weight, while the French, who consume(消耗) rich food, continue to stay thin? Now a research by Cornell University suggests how life style and decisions about eating may affect weight. Researchers concluded that the French tend to(往往,倾向于) stop eating when they feel full. However, Americans tend to stop when their plate is empty or their favorite TV show is over.

    According to Dr. Joseph Mercola, a health expert, the French see eating as an important part of their life style. They enjoy food and therefore spend a fairly long time at the table, while Americans see eating as something to be squeezed(挤出) between the other daily activities. Mercola believes Americans lose the ability to sense when they are actually full. So they keep eating long after the French would have stopped. In addition, he points out that Americans drive to huge supermarkets to buy canned and frozen foods for the week. The French, instead, tend to shop daily, walking to small shops and farmers' markets where they have a choice of fresh fruits, vegetables, and eggs as well as high-quality meats for each meal.

    After a visit to the United States, Mireille Guiliano, author of French Women Don't Get Fat, decided to write about the importance of knowing when to stop rather than suggesting how to avoid food. Today she continues to stay slim and rarely goes to the gym.

    In spite of(尽管) all these differences, evidence shows that recent life style changes may be affecting French eating habits. Today the rate of obesity — or extreme overweight — among adults is only 6%. However, as American fast food gains acceptance and the young reject(拒绝) older traditions, the obesity rate among French children has reached 17% — and is growing.

同类题5

二氧化硫是重要的工业原料,探究其制备方法和性质具有非常重要的意义.

(1)工业上用黄铁矿(FeS2,其中S元素为﹣l价)在高温下和氧气反应制备SO2:4FeS2+11O2═8SO2+2Fe2O3,该反应中被氧化的元素是____ (填元素符号).当该反应转移2.75mol电子时,生成的二氧化硫在标准状况下的体积为____ L.

(2)实验室中用如图1所示的装置测定SO2催化氧化为SO3,的转化率.(已知SO3熔点为16.8℃,假设气体进入装置时分别被完全吸收,且忽略空气中CO2的影响.)

①简述使用分液漏斗向圆底烧瓶中滴加浓硫酸的操作是____ .

②实验过程中,需要通入氧气.试写出一个用图2所示装置制取氧气的化学方程式____ .

③当停止通入SO2,熄灭酒精灯后,需要继续通一段时间的氧气,其目的是____ .

④实验结束后,若装置D增加的质量为m g,装置E中产生白色沉淀的质量为ng,则此条件下二氧化硫的转化率是____ (用含字母的代数式表示,不用化简).

(3)某学习小组设计用如图3装置验证二氧化硫的化学性质.

①能说明二氧化硫具有氧化性的实验现象为____ .

②为验证二氧化硫的还原性,充分反应后,取试管b中的溶液分成三份,分别进行如下实验:

方案I:向第一份溶液中加入AgNO3溶液,有白色沉淀生成

方案Ⅱ:向第二份溶液加入品红溶液,红色褪去

方案Ⅲ:向第三份溶液加入BaCl2溶液,产生白色沉淀

上述方案中合理的是____ (填“I”、“Ⅱ”或“Ⅲ”);试管b中发生反应的离子方程式为____ .