题干

有一批货物需要用汽车从生产商所在城市甲运至销售商所在城市乙,已知从城市甲到城市乙只有两条公路,且通过这两条公路所用的时间互不影响.据调查统计,通过这两条公路从城市甲到城市乙的200辆汽车所用时间的频数分布如表:

所用的时间(天数)

10

11

12

13

通过公路l的频数

20

40

20

20

通过公路2的频数

10

40

40

10

假设汽车A只能在约定日期(某月某日)的前11天出发,汽车B只能在约定日期的前12天出发(将频率视为概率).

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同类题2

阅读下面短文,掌握其大意,然后从各题所给的A、B、C、D四个选项中,选出可以填入空白处的最佳选项,并在答题卡上将该项涂黑。

    As I drove my blue Buick into the garage, I saw that a yellow Oldsmobile was 1too close to my space. I had to drive back and forth to get my car into the 2 space. That left 3 enough room to open the door. Then one day I arrived home 4 , and just as I turned off the engine, the yellow Oldsmobile entered its space — too close to my car, 5 . At last I had a chance to meet the driver. My patience had 6 and I shouted at her, “Can't you see you're not 7 me enough space? Park farther over.” Banging(猛推) open her door into 8 , the driver shouted back: “Make me!” 9 this she stepped out of the garage. Still, each time she got home first, she parked too close to my 10 . Then one day, I thought, “What can I do?” I soon found 11 . The next day the woman 12 a note on her windshield(挡风玻璃):

    Dear Yellow Oldsmobile,

    I'm sorry my mistress(女主人) shouted at yours the other day. She's been sorry about it. I know it because she doesn't sing anymore while 13 . It wasn't like her to scream 14 . Fact is, she'd just got bad news and was taking it out on you two. I 15 you and your mistress will 16 her.

Your neighbor,

Blue Buick

    When I went to the 17 the next morning, the Oldsmobile was gone, but there was a note on my windshield:

Dear Blue Buick,

    My mistress is sorry, too. She parked so 18 because she just learned to drive. We will park much farther over after this. I'm glad we can be 19 now.

Your neighbor,

Yellow Oldsmobile

    After that, whenever Blue Buick 20 Yellow Oldsmobile on the road, their drivers waved cheerfully and smiled.