* B
* *
* *
* *
* *
* A *
* *
* * C
* *
* *
* *
*********************** D
E
39) r+s+t 是偶数么?
(1)r+s是偶数
(2)s+t是偶数
69) 根号下0.0004=?
73) three people carry messages in the same amount of time at respective speed, A carries from place W to X at the speed of 100 miles per minute, B from X to Y at 80 miles per minute, C from Y to Z at 70 miles per minute. the points WXYZ are on a line and at the certain sequence, the distance from W to Z is 750 miles. What is the distance from X to Y?
阅读3:土星光环
第一段:某年起科学家对土星(Saturn)光环的起源的看法起了变化。原来以为它和土星(5 billion years ago)同时形成。但如果是那样,它应该比现在暗,像木星光环一样。因为宇宙中的漂移物质都是暗的。光环不断吸收这些物质会越来越暗。
第二段:新的假设是在500 million years ago,有一个主要成分是冰的星体,经过土星时被土星的引力拉散了,它的一部分形成了土星的光环。