题干

大家看过中央电视台“购物街”节目吗?其中有一个游戏环节是大转轮比赛,转轮上平均分布着5、10、15、20一直到100共20个数字.选手依次转动转轮,每个人最多有两次机会.选手转动的数字之和最大不超过100者为胜出;若超过100则成绩无效,称为“爆掉”.

(1)某选手第一次转到了数字5,再转第二次,则他两次数字之和为100的可能性有多大?

(2)现在某选手第一次转到了数字65,若再转第二次了则有可能“爆掉”,请你分析“爆掉”的可能性有多大?

上一题 下一题 0.0难度 选择题 更新时间:2015-11-18 02:51:07

答案(点此获取答案解析)

解:(1)由题意分析可得:要使他两次数字之和为100,则第二次必须转到95,因为总共有20个数字,所以他两次数字之和为100的可能性为20
1
(2)由题意分析可得:转到数字35以上就会“爆掉”,共有13种情况,因为总共有20个数字,
所以“爆掉”的可能性为{

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根据短文内容,从短文后的选项中选出能填入空白处的最佳选项,并在答题卡上将该项涂黑。选项中有两项为多余选项。

    When many people think about planting a tree, they do not realize that there are several things that they need to consider. You can't simply just dig a single hole, throw the tree into that space, and expect it to grow without any disease. ____

    The first thing that you need to take into account is the time of year that you are looking to plant the tree in. Believe it or not, in order to plant a tree that will stay alive and be able to survive, you have to plant it at the time of year that is right for the tree. ____ The burning sun during these periods of time will cause a big amount of stress of the tree, which will then lead to its death. ____

    ____ You should choose a suitable region and climate for the tree. If you decide to plant a tree that is not a native of a particular climate, you need to consider different factors about the tree such as the growth habits of the tree and how much tolerance the tree has to different weather conditions.

    ____ Sometimes in cases where people will be digging deep holes to plant a tree, they need to make sure that they are not digging around the phone lines that may be buried below the surface. Among other things, the hole determines if the tree can survive.

A. Normally you should never plant a tree in late spring or summer.

B. When digging a hole for a tree, you'd better dig as deep as possible.

C. You should then look at the place where you plan to plant the tree in.

D. The best time to consider planting your tree is around autumn or early spring.

E. The tree will not only be planted but will continue to grow well for years to come.

F. The next thing that you need to know is whether there are requirements where you'll dig.

G. There are a few basic things that you need to do in order to make sure the tree grows healthily.