假定某种商品价格从6.5元上升为7.8元，供给量是从13000单位增加为15500单位。需求量从14700单位减少为14200单位。 要求计算：(1) 在这段供给曲线范围内，供给弹性是多少(保留小数点后二位) (2) 在这段需求曲线范围内，需求弹性是多少(保留小数点后二位)
参考答案：
(1) σ=(△Qst/Qst)/(△Pt/Pt)＝[(15500-13000)/13000]/[(7.8-6.5)/6.5]
=0.96
(2) ηx=(△Qdt/Qdt)/(△Pt/Pt)=[(14200-14700)/14700]/[(7.8-6.5)/6.5]
=-0.17
| 完形填空。 | |||
| If you were in trouble, what would you do? Would you wait, ask for help or __1__ it by yourself? Once, a terrible flood (水灾) destroyed (毁坏) a village. A man was trapped (困住) in the flood. The water was all around him in front of a house, __2__ he was not very scared because he always believed in God. He thought God was coming for his safety. At that moment, a big wooden board came. If he caught it, the board would __3__ him out, but the man kept waiting for God. He didn't take a(n) __4__ at it at all. Then a small boat drifted (漂流) by, but the man still kept waiting and did nothing. The water was deeper and deeper. The two people in another boat were __5__ him and shouted to him, "Come on and go with us!" But the __6__ man stayed there and kept waiting for God. You can guess the result easily. The man died in the end. When he saw God in heaven, he complained to God, " _7 didn't you save me?" God said he had tried to save him. The big wooden board, the small __8__ , and the two men were all the things that he had sent to help him, but the man __9__ them. From this we can see that God helps those who help __10__. If you don't help yourself, God won't help you, either. | |||
| ( )1. A. cause ( )2. A. and ( )3. A. keep ( )4. A. pride ( )5. A. offered ( )6. A. bad ( )7. A. Why ( )8. A. house ( )9. A. received ( )10. A. themselves | B. deal B. but B. let B. look B. worried about B. friendly B. When B. wood B. refused B. herself | C. solve C. so C. help C. attention C. thanked C. confident C. Where C. boat C. hated C. himself' | D. aid D. though D. allow D. decision D. treated D. poor D. Who D. child D. loved D. yourselves |
