问题 解答题

10条线段,最多能有45个交点.______.

答案

设n条直线最多交点个数为M:

两条相交直线最多有1个交点,即n=2,M=1

三条直线最多有3个交点,即n=3,M=3

四条直线最多有6个交点点,即n=4,M=6

五条直线最多有10个交点,即n=5,M=10

则n条直线最多交点个数M=1+2+3+4+…+(n-1)=n(n-1)÷2,

所以,10条直线最多的交点为10×(10-1)÷2,

=10×9÷2,

=90÷2,

=45(个),

故答案为:√.

阅读理解

Dear Bridge of Hope supporters,

July 2010 was a productive month for the teachers at BOH. Marilyn traveled to Liberia and helped Kathleen Ngenda with her teacher training program on Basic Adult Literacy. During the eight-day training, she helped the teachers learn to pronounce, spell and write correctly. They are currently working on personal sets of cards and lists so that they can teach this concept to students in the fall. Kathleen plans on two trips back to the school to monitor teachers in their teaching.

Marilyn found a very dedicated (投入的)and enthusiastic group of elementary teachers who are focused on bettering themselves as educators. BOHUSA will offer financial support for their further educational studies this fall. Our goal is to have all staff be certified by the end of 2013.

The Liberian government recommends a C-certificate for teachers of elementary students, which can be obtained in one year of education classes (taken on Saturdays).

There is a great need to add seventh and eighth grade classrooms and a library. There is actually no room, however, and so we need to add a second floor. Currently the ground floor houses the church and the school uses this space for daily services. The first floor would give space for three more classrooms, in addition to a large reading room and computer labs. About $40,000 to 50,000 is required to meet the educational needs.

If you would like to contribute to this building project, please make out your check to:

Bridge of Hope

12002 Arnold Rd.

Orrville, Ohio 44667

Bridge of Hope Foundation is a non-profit organization. You do not have to pay tax on your contributions.

小题1:Marilyn went to Liberia to ______.

A.take a trip

B.visit a school

C.take training classes

D.help train teachers小题2:What do we know about the school from Paragraph 4?

A.It needs repair

B.It needs expansion

C.It has no office.

D.It has an old library,小题3:The purpose of the letter is to _________.

A.show the achievements of BOH

B.thank BOH supporters for their concern

C.raise money for an educational project

D.call people’s attention to education in Liberia

单项选择题