同学们，在你们的数学学习中是否和我一样，有一些不经意的发现？现在我就来介绍我的几个发现。
如果要你算一个多位数乘5，你是不是准备列竖式？我却可以口算，因为我发现一个小诀窍。想知道吗？让我来告诉你：算485325的积，先找到这个数485320，再把它除以2，你会口算吗？242660这就是485325的积了。知道为什么吗？我把原来的数先扩大10倍，再缩小2倍，是不是相当于扩大5倍呀？你掌握这个小窍门了吗？
同样的发现我还有：一个数乘1.5只要用它本身加上它的一半就可以了。（想想为什么？）一个数乘15呢？用刚才的方法再加一步你已经想到了吧，再扩大10倍就好了！
我还发现一个多位数，末两位符合这个要求：十位上十奇数，个位上是5，用它乘5，积的末两位肯定是75。我想这是为什么呢？因为多位数的个位与5相乘得25，积的个位是5，向十位进2，而十位的奇数与5相乘的到的是几十五，这个5应该和个位进上来的5相加写在十位上，所以这个积的十位上肯定是7，个位上肯定是5。同样的道理，你不难推出，一个多位数十位上是偶数，个位上是5，它与5相乘，积的末两位肯定是25。
这个发现能用我前面所说的一个数乘5的巧妙算法来解释吗？想想看，它们是一致的，因为这个数扩大10倍后，末两位是50，再除以2，可能百位上有余数1，与50合起来1502=75是末两位上的数字，也可能百位上没有余1，那么502的商就是末两位上的数字。
同学们，我的这个小发现是不是很微不足道？但我很自豪，这是我自己动脑筋观察和思考的结果。伟大的发现不是由这点点滴滴组成的吗？同学们，让我们一起做一个勤于思考、善于发现的人吧！
谈谈对零的认识
零看上去很单调，就是没有，其实它非常地丰富，它隐藏了许多。在数学中零非常特殊，不管做什么题，你应该考虑零。
在几何中，0经常被作为记号。
0的特殊源于在一些概念或题里，比如每个有理数都有倒数，0却没有，有理数分为正数、负数。0，一个数就分为一类，这不特殊吗？在除数里，只有零不能作除数。零作被除数，不管除以什么数(0除外)都得零。
往往我们会忽视零，但它却起着重要的责任。如，问等于几？有些人就不能联想到0。在数数时，有人就会忘掉零。如：不大于5不小于-5的整数有几个？有人就会定有8个。其实还有0。如：有哪些数的绝对值不大于本身？那就是正数和零(也可以称之为非负数)。
零在生活中更量五彩斑斓。在期末后开家长会，老师那里登记的犯错本给家长看时，我们都希望自己的那一格记着0，这表示我们没有犯过错，家长高兴，我们高兴。但是在卷子上我们都不希望看到这个数或接近这个数的整正数，否则回家的日子就难过了。在比赛中，谁都不希望得到0。
零是丰富的。我认为零在题中是陷井，大家以后做题时应考虑零。零在不同的场合也能使人的情绪改变。它是美妙而又丰富的。
对0的认识
0是一个奇妙的数字，又是一个中学生经常遇见的老朋友了，计算，概念，都要遇见。
首先，0表示什么也没有，简直可称得上是数字里面的沙漠，0也是一个奇怪的数字，放在体积、面积、重量、速度、路程等所有单位里面，都表示没有，以表示时间、一个人的年龄、赛跑的刚开始、起点。
it was the first day of our winter holiday. all of us were
very happy. why? because we have one months to do things we
love to do. we are free. although we have some homework. but
we can finish them in several days. and the rest time we can
make good use of. my god! we have been very tired after hard
studying. in winter holidays, i want to have full sleep and
eat good food in order to replenish myself. last but not the
least, i will have a good rest.
january 14 XX
it was the second day of our winter holiday. i felt good. i
felt im free. i had a lot of time to do things i like. my
parents are in beijing. so i live alone but i dont feel
lonely. but i didnt do something special. i stayed at home
and watched tv. oh! i wrote an english daily composition. it
was my homework. today, i have slept for 14 hours. i thought i
was very tired. it was time for dinner. i must go! i am very
hungry.
january 15 XX
it was the third day of our winter holiday. today, there are
many business in my mothers company. so my mother told me to
help my uncle who is the manager of my mothers company. i sat
in my mothers office and help her answer the telephone. while
i was free, i was writing my homework. although i also have a
lot of time to do my homework, i still do it. because in my
mothers office, i had nothing to do. if i did nothing, i was
wasting my time and my life. i cant do the foolish thing. we
should take good use of our time.
january 16 XX
it is a special day today. my mother sent one hundred basket
of red bayberries. i like to eat red bayberries. it tastes
nice. when they arrived in shanghai, they were still fresh.
but most of them would be sent to my mothers business
friends. i chose the best basket of red bayberries to eat. i
put the rest in my refrigerator. red bayberry is my hometowns
special product. it is well-known in china. many people like
to eat it.
january 17 XX
today, i still went to my mothers office. my mother was very
busy, so was my father. they always live in beijing. they must
get up early. because they will manage the factory. so i know
they are very laborious. so i should save my money. also i
should help them. although i cant do something useful, but i
think i should share the work with them. i am one of my family
member. in the future, i will take a job and work. it time
for me to begin to learn how to work.
january 18 XX
i have rested for a week. i began to feel bored. so i went out 共7页，当前第1页1234567
暑假过了一半了，但已经发生了许多事情。我先从暑假刚开始说起吧，一放暑假我们就要韩国了。我一登上豪华游轮，我赞叹就一个接着一个。接着我们来到了我们的房间，整理好自己的衣物后，我就找我的好同学玩。游轮上面的活动很多，我在上面玩的很开心。我们还去了济州岛和釜山，但游轮之旅很快就结束。
过了几天，回到妈妈家，我听到他们说，要去金山城市海滩玩。我高兴地不得了。我期待的那天终于到了，我们整理东西准备出发。在路上我正想着怎么跟妈妈打水仗呢。到了那，我看见了金光闪闪的沙滩，我忍不住想去海里玩耍。一切就绪，我向海里奔过去。泡在水里就是舒服，我跟妈妈在水里玩耍。最后，要不是妈妈叫我走，我还舍不得走呢。可是谁知道回到家，手臂和后背发红、发痒。过了几天，手臂和后背还发红、发痛，最后，居然蜕皮了。我被晒黑了。真是一个难忘的回忆。
回到奶奶家后，爷爷跟我说：“爸爸打来一个电话，讲7月27日去玛雅海滩水公园。”我听了快要跳起来了。我千等万等终于等到了那一天。这次全部带好了，少不了防晒霜和衬衫。准备出发，先去姐姐家，等姐姐全部搞好我们就出发了。我们在车上坐了很久。我们终于到了。我和姐姐到女更衣室换泳衣，跟爸爸碰头后。我们玩水上滑滑梯、大冒险........我们玩好后，直接去宾馆了。我们休息了一会儿，去室内游泳池游。吃好晚饭后我们看了一会儿电视，就睡着了。第二天，我们就走了。半个暑假就去了这么好玩的地方，我真开心！真想知道剩下的半个暑假还有什么好玩的等着我，好期待呀！
