问题 单项选择题

现有一批零件给甲、乙、丙三个车间做,甲、乙两个车间合作比乙、丙两个车间合作要多花25%的时间,甲、丙两车间合作需要10天完成。若甲、丙的工作效率比为5:7,则三个车间合作需要多少天完成全部零件

A.6
B.8
C.10
D.12

答案

参考答案:B

解析: 设甲、丙每天分别完成5、7个零件,则总零件数为(5+7)×10=-120个。设乙每天完成x个零件,由于甲、乙合作比乙、丙合作要多花25%的时间,则甲、乙的效率和与乙、丙的效率和之比为1:(1+25%)-4:5.即(5+x):(x+7)=4:5,解得x=3。故三个车间合作需要120÷(5+3+7)=8天。

阅读理解

阅读理解。

     New York times, Nov, 24,2011-It is not just any bug, but the native nine-spotted ladybug.

And its reappearance is something of a relief, because it is the official New York State insect,

even though the last recorded sighting of it in New York was 29 years ago.

     Its absence had not gone completely unnoticed. There was a moment in 2006 when the State

Assembly, realizing that the state insect had left the state, tried to replace it with a different species

of ladybug, an attempt that fortunately gave in to law.

     And now-after all these years-the state insect has been found. Like so many other New Yorkers,

it was seen summering in Amagansett. Peter Priolo, a volunteer participant in an effort called the

Lost Ladybug Project, found the ladybug on July 30 in a patch of sunflowers during a group search

he had organized.

     "I didn't realize it was a nine-spotted when I found it," Mr. Priolo said. He was on his way to do

an end-of-the-day ladybug record, so, he said, "I put it in my jar and hurried back to meet with

everybody."

     If the ladybugs are making a comeback, it is only beginning. The lost Ladybug Project started

surveys in 2000. As of 2006, only five nene-spotted ladybugs had been found in North America in

the previous 10 years, none of them in the East. Then one lone ladybug was found in Arlington,

Va. None had been found in the East since, and only 90 have been reported in North America.

     After scientists at Cornell confirmed Mr. Priolo's find, they went to the Amagansett farm in

mid-August to lead a search that turned up about 20 more of the bugs. An area between rows of

carrots and beans turned out to be a hot spot. "We found a lot of them on cosmos and zinnias," said

Dr. Losey said, an insect expert. The farm is part of the 10,000-acre Peconic Land Trust in Amagansett,

and it is organic. For ladybugs, Dr. Losey said, "you couldn't design a better place."

     Dr. Losey wants to find out if it makes sense to reintroduce this strain of the ladybug in other areas.

And he expects volunteers to be back out in the field when ladybug season starts again in the spring.

Now, he said, "we need to find out more places where there are just as many."

1. The last time the New Yorkers saw their state insect in            .

A. 2000

B. 2006

C. 1998

D. 1982

2. The New Yorkers are so delighted to see the insect because           .

A. it has some bright spots on its back

B. it is the official insect of the city

C. it had been out of sight for quite some time

D. it is a new species unknown to New York

3. What does the second paragraph of the passage imply?

A. It's against the law to bring new insects to New York.

B. The State Assembly don't like to live with Ladybugs.

C. The absence of the state insect had never been known.

D. The state insect had to leave because of a new species.

4. From the last two paragraphs we know that       .

A. only some insect experts are really interested in ladybugs

B. Dr Losey is quite confident about the future of the insect

C. most ladybugs have m moved to live in the down area

D. more vegetables will be grown to welcome the state insect

单项选择题