题干

一艘轮船从甲港开往乙港,由于顺水,每小时可以航行28千米,3小时到达.这艘轮船从乙港返回甲港时,由于逆水,每小时只能航行21千米.这艘轮船往返一次每小时的平均速度是(  )

A:12千米  

B:24千米  

C:24.5千米

D:25千米

上一题 下一题 0.0难度 选择题 更新时间:2011-12-15 01:00:41

答案(点此获取答案解析)

B

同类题1

阅读理解

Jack had an unusual experience last night. He is sharing it with his friends. Ken and May.

Ken: What were you doing, Jack What did you see

Jack: It was half past nine last night and I was getting ready for bed. I heard some strange noise outside while I was brushing my teeth. I wondered what was happening and I went to the window and looked out. To my surprise, I saw a bright yellow green light in the sky.

May: Maybe the light you saw was a UFO! Or a ghost! A few years ago, an American man saw a flying saucer while he was driving along a road. He also saw some strange yellow light. You have heard about it, haven't you

Ken: Don't be imaginative, May. Jack didn't see anything, or anybody. It wasn't a ghost. It was probably a plane, or a shooting star .Perhaps Jack just made a horrible dream!

Jack: I am very serious .I did see something. The light disappeared and then suddenly some “tiny people” were standing in the garden .There were four of them .Two of them ate some flowers in the garden .It was always stretching out its arms.

Ken: Oh, come on, Jack. I really doubt what you have said.

Jack: I am not joking! One of the people was looking at me through the window.

May: Really What did it look like Were you frightened

Jack: Its whole body was green. It had no ears and nose. Its hands were huge. Its eyes were very big and resembled eggs. It started at me and I could hardly move.

Ken: What happened then ?

Jack: I was able to move eventually. I ran and got my camera immediately.

May: And......

Jack: I didn't have a film.

May: Oh no!