问题 解答题

小张和小王要加工同样多的零件,用旧机床每小时加工20个,后来工厂为他们改换了新型机床,每小时加工60个.小张改换机床前后所完成的零件数的比为2:3,小王改换机床前后的时间比为3:2.结果小王比小张少用18分钟完成任务.他们每人完成了多少个零件?

答案

:设小王所用时间为3t:2t,

故零件总量为:20×3t+60×2t=180t (个),

小张作的零件:旧机床为180t×

2
5
=72t (个),新机床为180t×
3
5
=108t(个),

小张用时:72t÷20+108t÷60=

27
5
t,

二人时间差:

27
5
t-(3t+2t)=
18
60
,得t=
3
4

故总零件:20×3t+60×2t=180t=180×

3
4
=135 (个);

答:他们每人完成了135个零件.

单项选择题
单项选择题

If there is one thing scientists have to hear, it is that the game is over. Raised on the belief of an endless voyage of discovery, they recoil from the suggestion that most of the best things have already been located. If they have, today’s scientists can hope to contribute no more than a few grace notes to the symphony of science.

A book to be published in Britain this week, The End of Science, argues persuasively that this is the case. Its author, John Horgan, is a senior writer for Scientific American magazine, who has interviewed many of today’s leading scientists and science philosophers. The shock of realizing that science might be over came to him, he says, when he was talking to Oxford mathematician and physicist Sir Roger Penrose.

The End of Science provoked a wave of denunciation in the United States last year. "The reaction has been one of complete shock and disbelief, "Mr. Horgan says.

The real question is whether any remaining unsolved problems, of which there are plenty, lend themselves to universal solutions. If they do not, then the focus of scientific discovery is already narrowing. Since the triumphs of the 1960s—the genetic code, plate tectonics, and the microwave background radiation that went a long way towards proving the Big Bang—genuine scientific revolutions have been scarce. More scientists are now alive, spending more money on research, that ever. Yet most of the great discoveries of the 19th and 20th centuries were made before the appearance of state sponsorship, when the scientific enterprise was a fraction of its present size.

Were the scientists who made these discoveries brighter than today’s That seems unlikely. A far more reasonable explanation is that fundamental science has already entered a period of diminished returns. "Look, don’t get me wrong," says Mr Horgan. "There are lots of important things still to study, and applied science and engineering can go on for ever. I hope we get a cure for cancer, and for mental disease, though there are few real signs of progress.

There have not been many genuine scientific revolutions in the past few decades because()

A. there have been decreased returns in the research of fundamental science

B. there are too many important things for scientists to study

C. applied science and engineering take up too much time and energy

D. today’s scientists are not as intelligent as those in the past