數學高手入黎!!!!!!!!!!!!!!!

2007-12-23 9:12 pm

1.which of the following equations does not contain like term?
A.3n2-1=8 B.2n=8 C.[(1/2)n]+[(1/2)n]=1 D.2n+2=-3n
2.solve the equation 3x-3=6(7-2x)
3. solve the equation 5(k-1)-3(k+1)=10
4. solve the equation 4m-2=4m-(18-4m)+12
5. solve the equation 3x-14=(2/5)(8x-6)

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6.lily had $200.she bought a number of pensk,each of which costed $5.she also bought a number of drawing pens,each of which costed $9.the number of pens was 2 times of that of drawing pens.after paying the bill,Lily still had $105.how many drawing pens did she buy?

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7.the perimeter of a rectangle is 26cm.if the length of this rectangle is reduced by 1cm and its width is increased by 2cm,it will become a square.what is the original length of this rectangle? A.7cm B.8cm C.9cm D.10cm

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8.Mrs Cheung bought home a box of apples.if each family member could get 3 apples,3 apples would be left.if each family member got 4 apples,2 more would be required. (a)how many people were there in Mrs.Cheung’s family? (b) how many apples did a box contain?

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9.in a toy factory,each worker produce 12 pieces of toys per day on average.in order to reproduce 10500 pieces of toys,the factory assigned a number of workers to complete the project. In order to boost up the speed of the production,the number of workers was

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increased by half after 10 days.5 more days later,the project was completed.how many workers worked for the project before the factory assigned more workers? 10.Yvonne bought a sweater,a pair of jeans and a pair of shoes in a department

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store.she spent $450 in total.if the price of the pair of jeans was 2 times of that of the sweater and the pair of shoes was $45 more expensive than the sweater,find the price of the sweater.

回答 (1)

VIŃCĘÑT

2007-12-23 11:37 pm

✔ 最佳答案

1. I am sorry I do not know the answer
2. 3x-3=6(7-2x)
x-1=14-4x
5x=15
x=3
3. 5k-5-3k-3=10
2k=18
k=9
4. 4m-2=4m-(18-4m)+12
4m-2=4m-18+4m+12
4m=4
m=1
5. 3x-14=(2/5)(8x-6)
15x-70=16x-12
x=-58
6. Let x be the number of pens, thus , y be the number of drawing pens,
200-(5x+9y)=105-------------α
x=2y--------------β
Substitute β to α,
200-(10y+9y)=105
19y=95
y=5
∴She bought 5 drawing pens.
7. Let x be the length of rectangle, y be the width, the two equations can be obtained as follows,
2(x+y)=26
x+y=13
y=13-x-------------α
x-1=y+2-------------β
Substitute α into β,
x-1=13-x+2
2x=16
x=8
∴So the original length of the rectangle is 8 cm, hence the answer is B.
8a. Let x be the total of those apples, and y be the number of family members,
hence these equations can be obtained,
x-3y=3
x=3y+3-----------α
x-4y=-2----------β
Substitute α into β,
3y+3-4y=-2
y=5
∴There are 5 members in Mrs. Cheung's family
8b. Substitute y=5 into β,
x-20=-2
x=18
Hence there were 18 apples in the box
9. Let x be the number of workers, y be the number of toys produced, z be the time
so we obtain y=12xz
There are y toys produced by a original number of workers within 10 days, so we obtain
y=12x(10)
y=120x------------α
Then the project was completed, the remained toys 10500-y has been produced by increased number of workers x(1+0.5) within 5 days, so we obtain,
10500-y=12x(1+0.5)(5)
10500-y=90x------------β
Substitute α into β,
10500-120x=90x
x=50
∴The original number of workers before the increase is 50
10. Let x be the price of sweater, y be the jeans and z be the shoes,
x+y+z=450-----------α
y=2x-----------β
z=x+45----------------γ
Substitute β and γ into α,
x+2x+x+45=450
4x=405
x=101.25
∴The price of the sweater is $101.25

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