题干

小明去超市买三种商品.其中丙商品单价最高.如果购买3件甲商品、2件乙商品和1件丙商品,那么需要付费20元,如果购买4件甲商品,3件乙商品和2件丙商品,那么需要付费32元.

(1)如果购买三种商品各1件,那么需要付费多少元?

(2)如果需要购买1件甲商品,3件乙商品和2件丙商品,那么小明至少需多少钱才能保证一定能全部买到?(结果精确到元)

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答案(点此获取答案解析)

解:(1)设一件甲商品x元,乙y元,丙z元,

根据题意得:3x+2y+z=20①

4x+3y+2z=32②

①﹣②得:﹣x﹣y﹣z=﹣12,

∴x+y+z=12,

答:如果购买三种商品各1件,那么需要付费12元;

(2)设需要购买1件甲商品,3件乙商品和2件丙商品,那么小明至少需m元才能保证一定能全部买到,由题意可得:

x+3y+2z≥m,

由(1)可知4x+3y+2z=32,

∴3y+2z=

同类题2

阅读下面文章,然后从文后所给的A—F选项中选择正确的小标题,将其序号填入题中。其中有一项是多余选项。

A. Animals on the Road

B. Keep Left

C. Crossing “Give Way” Rule

D. Traffic information

E. One Lane Bridges

F. Seatbelts

    Driving around New Zealand may be different from your own country. It's necessary for you to know more traffic information if you are traveling to New Zealand. Here are some tips to help you drive safely in New Zealand.

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    In New Zealand, traffic goes on the left side of the road and the driver sits on the right of the car. You should be careful to the left side while turning.

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    In general, driving in New Zealand is stress free. The only major difference is the “give way to the right'rule. This meant that if you were turning left, you had to give way to vehicles turning right into the same lane. 

    It is important to note that anyone behind a give way sign must give way to any cars on roads. Failure to give way will result in a $ 150 fine.

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    Many roads in New Zealand have one lane bridges on them. At one lane bridges, cars traveling in one direction must give way to cars going in the other one.

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    Pay more attention to farm animals on the road, especially in the countryside. On seeing them, you should stop and let the animals go past you or follow the farmer's instruction.

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    The seatbelts must be worn by the drivers. If you are caught not wearing your seatbelts, you will be fined.

All the tips above are necessary for a stranger to New Zealand.