某镇有A、B两家纯净水销售站，它们所提供的纯净水的价格、质量都相同．为了促销，A站的纯净水每桶降价20%销售；B站规定：每个用户购买B站的纯净水，第1桶按照原价销售，若用户继续购买，则从第2桶开始每桶降价25%销售，促销活动都是三个月．若小明家预计三个月要购买12桶纯净水，请你帮他判断购买哪家的纯净水较省钱，并说明理由．
解：设每桶纯净水的原价为a元，则购买12桶纯净水，
在A站需花费的金额为（1﹣20%）a·12=9.6a（元）；
在B站需花费的金额为a+（1﹣25%）a·11=9.25a（元）；
∵9.6a＞9.25a，
∴小明家应选择到B家纯净水销售站购买纯净水，这样较省钱．
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 There is an American story about three sisters. They loved each other very much. Each 1 could only be happy when she was with her sisters. The oldest sister stood 2 . Her name was Corn. Corn was beautiful and strong. The middle sister liked to twine (缠绕) 3 her sister Corn. Her name as 4 . As Bean grew taller, she could give Corn a 5 hug(拥抱). The youngest sister was very brave. She stayed at the 6 Of Corn and Bean to protect them from danger. Her name was Squash. When one of the sisters grew, 7 two wanted to grow. They 8 wanted to be alone. So they always 9 together in the same field. On summer nights, when stars shone in the sky, the three sisters changed into young girls. They were 10 green clothes, danced happily, and sang to their Mother Earth and their Father Sun. | |||
| ( )1. A. sisters ( )2. A. small ( )3. A. in ( )4. A. Corn ( )5. A. big ( )6. A. back ( )7. A. other ( )8. A．never ( )9. A. lives ( )10. A. in | B. family B. short B. around B. Bean B. bigger B. top B. the others B．always B. live B. on | C. sister C. fat C. at C. Squash C. small C. middle C. the other C．often C. lived C. at | D. brother D. tall D. from D. Mother D. smaller D. feet D. others D. sometimes D. living D. for |