一道七年级下册的数学题(二元一次方程应用题)
一、一道七年级下册的数学题(二元一次方程应用题)
据以往的统计资料，甲、乙两种作物的单位面积产量的比是1：1.5 ，现要在一块长200米，宽100米的长方形土地上种植这两种作物，怎样把这块地分为两个长方形，使甲、乙两种作物的总产量的比是3：4（结果取整数） 解：长方形土地面积S=200*100=20000（M^2） 设种植甲种作物的面积为S1，种植乙种作物的面积为S2，由已知得下方程组： S1+S2=20000 ......(1) （1*S1）/(1.5*S2)=3/4 ......(2) 解上方程式组,得 S1=10588.24（M^2）,取整数S1=10588（M^2）, S2=9411.76（M^2）,取整数S2=9412（M^2）, 面积划分 取整数S1/200=10588/200=53(M),53*200=10600(M^2) 取整数S1/100=10588/100=106(M),106*100=10600(M^2) 故把这块地分为两个长方形方法为:在这块地长200米的两边量取各106米,设分别为A、B两点，连接AB，沿AB划界即可。这样种植甲种作物长106M,宽100M；种植乙种作物长100M,宽94M。 10600*1/(9400*1.5)=106/141,106/141约等于3/4 答:在这块地长200米的两边沿同一方向（如由东向西）量取各106米,设分别为A、B两点，连接AB，沿AB划界,这样种植甲种作物的长方形为:长106M,宽100M; 种植乙种作物的长方形为:长100M,宽94M, 可使甲、乙两种作物的总产量的比是3：4（结果取整数）. 可以假设甲、乙两种作物的单位面积产量分别为1和1.5 总面积为200*100=20000m^2, 设给甲作物划出面积X,乙的为Y, 有X+Y=20000,(1*X):(1.5*Y)=3:4(也可写作1*X/(1.5*Y)=3/4) 可得X=180000/17,Y=160000/17
二、数学思维拓展题
1/2=1-1/2 1/6=1/2-1/3 1/12=1/3-1/4 1/20=1/4-1/5 1/30=1/5-1/6 1/42=1/6-1/7 1/56=1/7-1/8 1/2+1/6+1/12+1/20+1/30+1/42+1/56 =1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8 =1-1/8 =7/8 如果每人多分一个苹果，即每人可得6个苹果 因为苹果个数是桃子的3倍， (因为每人分5个苹果和2个桃子，最后正好把桃子分完) 所以应该刚好分完 实际每人分5个苹果时剩了11个 所以应有11个人 原来有苹果：11×5+11=66个 原来有桃子：11×2=22个
三、六年级比和比例题！！加分！！
若cc=ab,那么c叫做a与b的_因数
2x：3=(x-1)：4 ，算出X= —1（负1）
选择 1B 2 C
四、一、单选题（共 20 道试题，共 60 分。）
一、单选题（共 20 道试题，共 60 分。）
1. Your _D__ at the meeting will be a great support to our cause,says the cable.
A. absent
B. absence
C. present
D. presence
满分：3 分
2. When the sound of a gunshot _C__ nearby, the crowd ran for safety.
A. crack
B. cracker
C. cracked
D. cracking
满分：3 分
3. The child ran along, trying to _D__the adults.
A. set the pace
B. pace up
C. pace
D. keep pace with
满分：3 分
4. The child stumbled _B__ a stone and fell.
A. across
B. over
C. on
D. upon
满分：3 分
5. The speaker wander _B__off the point.
A. off
B. away
C. in
D. along
满分：3 分
6. They always __D_ their parents when they have trouble.
A. lean towards
B. lean to
C. lean
D. lean on
满分：3 分
7. Now all we can do is to help ourselves and _A__ to God.
A. pray
B. prayer
C. prey
D. preyer
满分：3 分
8. Many young girls like to __C_ a diary for recording their private thoughts and feelings.
A. write
B. take
C. keep
D. bring
满分：3 分
9. It is about time we _A__ his errors to him.
A. pointed out
B. pointed at
C. pointd forwards
D. came to the point
满分：3 分
10. Parents can not be __D_ about their children's future.
A. concern
B. concerned
C. unconcern
D. uncerned
满分：3 分
11. The house is in the __B_ of being built.
A. procedure
B. process
C. proceed
D. procession
满分：3 分
12. For my own part ,everything is O.K. I have nothing to __A_ of
A. complain
B. complaining
C. complaint
D. complained
满分：3 分
13. Last night's fire was the worst __B_ that has ever hit the frontier town.
A. disease
B. disaster
C. danger
D. dangerous
满分：3 分
14. An employee's __B_ to report to work on time ,if habitual, may lead to his or her dismissal.
A. fail
B. failure
C. fall
D. falling
满分：3 分
15. The doctor _A__what to do with the case because he couldn't detect the cause of the illness.
A. was puzzled
B. was puzzling
C. was puzzle
D. was puzzlingly
满分：3 分
16. He committed an _D__against the law.
A. offend
B. offender
C. offensive
D. offence
满分：3 分
17. A __A_ of travellers are expected to arrive soon.
A. company
B. business
C. firm
D. fellowship
满分：3 分
18. It took him three days to _A__upon our proposal before he gave us the answer.
A. reflect
B. return
C. resume
D. respond
满分：3 分
19. Having practiced for so long ,the New York baseball team D___of the winning the World Series this year.
A. make a chance
B. gets a chance
C. brings a chance
D. stands a chance
满分：3 分
20. Every day, on the lawn in front of the county court, we hoisted the national flag at daybreak and __A_it at sunset.
A. lowered
B. low
C. lowed
D. lower
满分：3 分