题干

某体育用品商场采购员要到厂家批发购进篮球和排球共100只,付款总额不得超过11815元,已知两种球厂家的批发价和商场的零售价如下表,试解答下列问题:

品名厂家批发价(元/只)市场零售价(元/只)
篮球130160
排球100120

⑴该采购员最多可购进篮球多少只?
⑵若该商场把100只球全部以零售价售出,为使商场的利润不低于2590元,则采购员采购的方案有几种?

上一题 下一题 0.0难度 选择题 更新时间:2019-02-22 05:10:26

答案(点此获取答案解析)

解:(1)设采购员购进篮球x只,根据题意得:
130x+100(100-x) ≤11815,
解得x≤ 60.5,
因为x为正整数,所以x的最大值时60,
答:采购员最多购进篮球60只;
(2)设采购员购进篮球x只,根据题意得:
30x+20(100-x) 2590≥2590,
解得x≥59,
所以x=59或60,
答:采购员购进方案有两种:购进篮球59个,排球41个或购进篮球60个,排球40个.

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    When kids believe they can achieve success in math and reading, they are more likely to achieve high test scores in those subjects, new research suggests.

    Researchers used one US data set (1,354 American children) and one UK data set (13,901 British children) to measure self-concept and standardized assessments of early and later academic achievement. Self-concept is how students perceive(感知)their abilities to succeed on academic tasks. The data involved youth aged 5 to 18.

    The study considered children's earlier achievement and their characteristics and backgrounds, including birth weight, race, gender, age, and their mother's education.

    The researchers found that children's self-concept of their ability in math predicted later math achievement, while their self-concept of their ability in reading predicted later reading achievement.

    The finding suggests that the links between self-concept of ability and later achievement are specific to areas; that is, there is a link from students' self-concept about reading to reading achievement, and from students' self-concept about math to math achievement.

     “It is not unusual to see standardized measures of achievement predict achievement later in schooling, but it shows that there is more to understand.” says study coauthor Pamela Davis-Kean.

    The research also showed that success was not limited to students who perform at the top levels.

     “It involves in students with different levels of achievement in math and reading,” says Maria Ines Susperreguy, an assistant professor at Pontificia Universidad Catolica de Chile, who led the study. “Even the lowest-performing students who had a more positive view of their math and reading abilities had higher levels of achievement in math and reading.”

    Researchers say they don't know what parents or students did to create these beliefs, but it's an issue they will research further.