问题 单项选择题

有两只相同的大桶和一只空杯子,甲桶装牛奶,乙桶装糖水,先从甲桶内取出一杯牛奶倒入乙桶,再从乙桶取出一杯糖水和牛奶的混合液倒入甲桶,请问,此时甲桶内的糖水多还是乙桶内的牛奶多?()

A.无法判定

B.甲桶糖水多

C.乙桶牛奶多

D.一样多

答案

参考答案:D

解析:

解法一:分析法。假设大桶的容量是N杯,则第一次从甲取出一杯牛奶倒入乙桶之后,两桶中的物质分别为甲桶中有(N-1)杯牛奶,乙桶中有1杯牛奶和N杯糖水。均匀后,再从乙桶取出一杯糖水和牛奶的混合物倒入甲桶,这杯混合物中有牛奶1/(N+1)杯,有糖水N/(N+1)杯,因此乙桶中剩余的牛奶有N/(N+1)杯,而倒入甲桶中的糖水也有N/(N+1)杯。甲桶内的糖水和乙桶内的牛奶一样多。

解法二:最值法。如果杯子的容量与大桶里的牛奶、糖水的体积相同,那么相当于把甲桶的牛奶全部倒入乙桶,然后再从乙桶倒入甲桶一半糖水和牛奶的混合物,这时两桶中牛奶、糖水的体积均相同。

单项选择题
阅读理解

Ted doesn’t like cars. He wants people to stop driving because cars make the air dirty. Ted had an idea. He said,“I’m going to cycle around North America. I want to show everyone that cycling is a fun way to get around. If more people ride bikes, the air will be cleaner.”

He left his hometown with $160 in his pocket. When he got to San Diego, he met another cyclist. The cyclist invited Ted to speak at a big meeting about the environment. He said,“We’ll pay your airfare to Texas and we’ll pay you to talk about your cycling trip.”Two hours later, Ted was on a plane to the environmental conference and to a big surprise!

While he was at the conference, he met Deanna. It was love at first sight! They talked for six hours straight.

The next day, Ted called Deanna and asked her to finish the trip with him. Deanna said yes, sold everything in her apartment, gave her notice at work, and was on the road with Ted 20 days later!

“It was difficult at first,”said Deanna. “Ted got up every morning at 6:00 a.m., but I wanted to sleep until noon.”After a few days, they started having fun. As they cycled from Florida to Montreal and then back to Vancouver, every day was an adventure. People paid for their food in restaurants and gave them extra money. Some people gave them $50 or $100. They slept in people’s backyards and drank beer with motorcycle gangs.

On their way back to Vancouver, they stopped in Edmonton to visit Ted’s relatives. During the stopover, they got married. People tied a “Just Married”sign and tin cans to the backs of their bikes. They now want to write a book about their trip. “We want people to know that you can be an environmentalist and still have fun, ”Ted said.

小题1: Ted got paid for ______.

A.giving a talk about his cycling trip

B.cycling throughout North America

C.traveling around North America by air

D.attending conferences on cycling小题2: The “big surprise” he had at the conference was that _______ .

A.he met another cyclist who wanted to join him

B.he fell in love with a girl there

C.he gave a long talk lasting 6 hours

D.he had a lot of fun talking about his cycling trip小题3: The underlined part “gave her notice at work” probably means __________ .

A.Deanna was fired by her boss for not going to work

B.Deanna asked for a long leave from work to join Ted in his trip

C.Deanna told people beforehand that she would leave her job

D.Deanna handed in the notice that she were asked to finish before小题4:During the trip, Ted and Deanne ___________.

A.found it hard to get up early

B.were attacked by motorcycle gangs

C.never pay for their meals in restaurants

D.got married