体育中心要建造一个长方体形状的儿童游泳池,长40米,宽14米,深1.2米

解题思路：用张宇家到体育中心的路程加体育中心到图书馆的路程，求出张宇从家骑车经过体育中心到图书馆的路程，再根据速度=路程÷时间，求出张宇骑车的速度，然后再除21，就是需要的时间．

21÷[（9+15）÷2]，
=21÷[24÷2]，
=21÷12，
=1.75（小时）．
答：需要1.75小时．

点评：
本题考点： 简单的行程问题．

考点点评： 本题主要考查了学生对路程、速度、时间三者之间数量关系的掌握情况．

楼主!
体育中心（For example,Olympic Centre）可以做很多事情啊
你想想就行：
swimming,playing basket ball,volleyball,football,table tennis,tennis,running,jogging,walking a dog...
你最好像这么介绍拿高分,从哪里进来,走几步路,左侧是什么,右侧是什么.
最后说这个体育中心还可以喝茶,喝咖啡,买东西（shopping/retails）（这很关键,因为不起眼的附加条件往往是体育中心的国际评判标准）,可以一句话概括.
It is not very difficult for you to form complicated sentences and illustrate your own statements.
Good luck to you and wish you a happy new year!

19680

（1）800÷2= 400（米）；2：（800×100）=1：40000；
（2）2.5÷ =100000（厘米）=1000（米）

30*25*2=1500立方米
30*25+25*2*2+30*2*2=750+100+120=970平方米
需要挖土1500立方米,瓷砖的面积是970平方米

解题思路：科学记数法的表示形式为a×10ⁿ的形式，其中1≤|a|＜10，n为整数．确定n的值是易错点，由于1 048 576有7位，所以可以确定n=7-1=6．有效数字的计算方法是：从左边第一个不是0的数字起，后面所有的数字都是有效数字．用科学记数法表示的数的有效数字只与前面的a有关，与10的多少次方无关．

55115=5.5115×10⁴≈5.51×10⁴．
故选：C．

点评：
本题考点： 科学记数法与有效数字．

考点点评： 此题主要考查了科学记数法的表示方法，以及用科学记数法表示的数的有效数字的确定方法．

has gone to
“去哪里”,表示正在那边

Notice
Attentions,please.The students of Grade Eight will go to Sports Center to watch a basketball match tomorrow.Please get together at half past eight at our school gate.Don't forget to wear the school uniforms.We are going there by bike.So please be careful.
Notice
Atention!The student of the eighth grade are going to watch a basketball match in the sports center tomorrow.All of you must get together at the school gate at 9 o'clock in the morming.All of you must wear school suit.And everyone had better prepare a bike.We wll ride a bike to go there.
任选其一哦.

解题思路：根据长方体的体积公式：v=sh，用水的体积除以游泳池的底面积即可．

2400÷（50×20）
=2400÷1000
=2.4（米）
答：水面到池底深2.4米．

点评：
本题考点： 长方体、正方体表面积与体积计算的应用．

考点点评： 此题主要考查长方体体积公式的灵活运用．

1》40×14×1.2=672m³
2》（40+14）×2=108m
答：要挖土672m³
至少有108m

C

16000立方米土,8720平方米瓷砖

Eighth-grade students watched Sports Center tomorrow to go to basketball games, 8:30 am at the school gate collection, required to wear school uniforms, riding a bike to go.或8 students to sports center to watch basketball tomorrow morning, 8: 30 set in the school gate, school uniforms, riding a bicycle.或Eight grade students will want to go to the sport center onlooking basketball game tomorrow, early morning 8:30 in the school front door mouth set, will request to put on the school uniform, will ride the bicycle to go.

Last Saturday,I went to the School Sports Center with my friends, we watched a Eighth Junior School ahd Eleventh Junior School's football match. In the moring, we went to the School Sports Center by b...

体育中心
sports cente

李叔叔的速度：4200/30=140
王叔叔的速度：4200/40=105
相遇时间：5+ （4200-105*5）/（140+105）=20分

设他骑车用了x小时,步行用了3/4-x小时
14x+4(3/4-x)=8
14x+3-4x=8
10x=5
x=1/2
3/4-x=1/4
他骑车用了1/2小时,步行用了1/4小时

sports cente

720乘以9除以6＝1080根

let's take them to sports centre.
compare to other places in beijing,the air in sun town is much less polluted.
i will ride to the town.
why don't you come and visit our theatre?
it took us 20 minutes to the town.

体育中心
sports cente

I am going to take to gym to play badminton.
I planed to take hin to ports center to play badminton.都行.呵呵