两个相似多边形的一组对应边分别为3cm和4.5cm，如果它们的面积和_爱下问搜题

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问题选择题

两个相似多边形的一组对应边分别为3cm和4.5cm，如果它们的面积和为78cm²，那么较大多边形的面积为（　　）

A．46.8cm²

B．42 cm²

C．52 cm²

D．54 cm²

答案

设较大多边形的面积为xcm²，则较小多边形的面积为：（78-x）cm²，

∵两个相似多边形的一组对应边长分别为3cm和4.5cm，

∴x：（78-x）=4.5²：3²，

解得x=54．

故选D．

完形填空

A passenger told an air hostess that he needed a cup of water to take his medicine when the plane just took off. She told him that she would 21 the water in ten minutes.
Thirty minutes later, when the passenger’s ring for 22 sounded, the air hostess realized it at once. She was kept so 23 that she forget to deliver him the 24 . As a result, the passenger was 25 to take his medicine. She hurried over to him 26 a cup of water, but to her surprise he 27 it.
In the following hours on the 28 , each time the air hostess passed by the 29 , she would ask him with a 30 whether he needed help or not. But the passenger 31 paid attention to her words.
When he was going to get 32 the plane, the passenger asked the air hostess to 33 him the passenger’s booklet(意见簿). She was very 34 . She knew that he would write down 35 words, which might result in the loss of her job. 36 with a smile she handed it to him.
Off the plane, she 37 the booklet and cracked a smile, 38 the passenger put it, “On the flight, you asked me whether I needed help or not for twelve times 39 . How can I refuse your twelve sincere smiles?”
That’s 40 ! Who can refuse twelve sincere smiles from a person?

单项选择题

调查某大学本科毕业生的就业情况时，研究者从该大学全体毕业生的花名册中抽取一定数量的样本。那么，全体毕业生的花名册是该次抽样的（）

A.总体

B.抽样单元

C.抽样框

D.样本