7．两个无理数的和不一定仍是无理数………………………………………………(　　 )

6．实数中既无最大的数又无最小的数………………………………………………(　　 )

5．有理数与无理数的积是无理数……………………………………………………(　　 )

4．因为－的绝对值是，所以绝对值等于的数一定是－…………(　　 )

3．算术平方根最小的实数是0………………………………………………………(　　 )

2．5.050050005是有理数……………………………………………………………(　　 )

1．两个正数，大数的平方根也较大 ………………………………………………(　　 )

17、(2007哈尔滨)青青商场经销甲、乙两种商品，甲种商品每件进价15元，售价20元；乙种商品每件进价35元，售价45元．

(1)若该商场同时购进甲、乙两种商品共100件恰好用去2700元，求能购进甲、乙两种商品各多少件？

(2)该商场为使甲、乙两种商品共100件的总利润(利润=售价进价)不少于750元，且不超过760元，请你帮助该商场设计相应的进货方案；

(3)在“五·一”黄金周期间，该商场对甲、乙两种商品进行如下优惠促销活动：

按上述优惠条件，若小王第一天只购买甲种商品一次性付款200元，第二天只购买乙种商品打折后一次性付款324元，那么这两天他在该商场购买甲、乙两种商品一共多少件？(通过计算求出所有符合要求的结果)

解：(1)设该商场能购进甲种商品件，根据题意，得

··························································································· 1分

乙种商品：(件)··················································································· 1分

答：该商品能购进甲种商品40件，乙种商品60件．

(2)设该商场购进甲种商品件，则购进乙种商品件．根据题意，得

······································································· 1分

因此，不等式组的解集为········································································· 1分

根据题意，的值应是整数，或或

该商场共有三种进货方案：

方案一：购进甲种商品48件，乙种商品52件，

方案二：购进甲种商品49件，乙种商品51件，

方案三：购进甲种商品50件，乙种商品50件．···························································· 1分

(3)根据题意，得

第一天只购买甲种商品不享受优惠条件　 (件)·································· 1分

第二天只购买乙种商品有以下两种情况：

情况一：购买乙种商品打九折，(件)

情况二：购买乙种商品打八折，(件)

一共可购买甲、乙两种商品(件)··························································· 1分

或(件)····································································································· 1分

答：这两天他在该商场购买甲、乙两种商品一共18件或19件．

16、(2007山东济南)某校准备组织290名学生进行野外考察活动，行李共有100件．学校计划租用甲、乙两种型号的汽车共8辆，经了解，甲种汽车每辆最多能载40人和10件行李，乙种汽车每辆最多能载30人和20件行李．

(1)设租用甲种汽车辆，请你帮助学校设计所有可能的租车方案；

(2)如果甲、乙两种汽车每辆的租车费用分别为2000元、1800元，请你选择最省钱的一种租车方案．

解：(1)由租用甲种汽车辆，则租用乙种汽车辆··········································· 1分

由题意得：·············································································· 4分

解得：········································································································· 5分

即共有2种租车方案：

第一种是租用甲种汽车5辆，乙种汽车3辆；

第二种是租用甲种汽车6辆，乙种汽车2辆．································································ 6分

(2)第一种租车方案的费用为元；

第二种租车方案的费用为元··············································· 7分

第一种租车方案更省费用．

15、(2007四川绵阳)绵阳市“全国文明村”江油白玉村果农王灿收获枇杷20吨，桃子12吨．现计划租用甲、乙两种货车共8辆将这批水果全部运往外地销售，已知一辆甲种货车可装枇杷4吨和桃子1吨，一辆乙种货车可装枇杷和桃子各2吨．

(1)王灿如何安排甲、乙两种货车可一次性地运到销售地？有几种方案？

(2)若甲种货车每辆要付运输费300元，乙种货车每辆要付运输费240元，则果农王灿应选择哪种方案，使运输费最少？最少运费是多少？

解：(1)设安排甲种货车x辆，则安排乙种货车(8－x)辆，依题意，得

4x + 2(8－x)≥20，且x + 2(8－x)≥12，

解此不等式组，得 x≥2，且 x≤4， 即 2≤x≤4．

∵ x是正整数，　∴ x可取的值为2，3，4．

因此安排甲、乙两种货车有三种方案：

(2)方案一所需运费 300×2 + 240×6 = 2040元；

方案二所需运费 300×3 + 240×5 = 2100元；

方案三所需运费 300×4 + 240×4 = 2160元．

所以王灿应选择方案一运费最少，最少运费是2040元．