Math application problems in the first year of junior high school Solving Urgent and anxious Emma ha

Scheme 1 calculates: 20 200 + 10 40 = 4400 Scheme 2 calculates: (20 200 + 30 40) 90% = 4680 Scheme 1 is cost-effective.

Option 1: Calculated payment = 20 200 + (x-20) 40 = 3200 + 40x Option 2: Calculated payment = (20 200 + 40x) 90% = 3600 + 36x 3200 + 40x = 3600 + 36x

x=100 100 ties, option 1 is more cost-effective.

When tie = 100, the call fee for option 1 is the same as that for option 2.

When there are more than 100 ties, option 2 is more cost-effective.

Solution: 1) When x = 30.

Scheme 1: 4000 + 40 (x-20) = 4000 + 400 = 4400 (yuan);

Scheme 2: 3600 + 36x = 3600 + 1080 = 4680 (yuan);

Therefore, it is more cost-effective to purchase according to option 1.

2）4000+40（x-20）；3600+36x；

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This question should be discussed in a categorical manner.

Set up a total of x discs to burn, and a total of y yuan is spent. If it is burned by the computer company, then y1=8x; If the school is self-engraved, then y2=120+4x

This is the time to compare. y1=y2

x=30 In this case, the two methods have the same fee.

y1 is greater than y2

x is greater than 30 at this time, choose to learn the key vertically and self-engrave.

y1 is less than y2

x less than 30 which is the option to burn to the computer company.

Hey. Xi Zhengzhou hopes to be helpful to you. This kind of question should be discussed in a categorical manner.

8x=120+4x

x=30 is less than 30 sheets, and the computer company burns the stool to save money.

In addition to 30 sheets, the cost of self-engraving is saved.

If it happens to be 30 tickets, the cost of both items is the same.

8x>120+4x

x>30

A: If it is less than 30 sheets, the computer company is suitable for engraving, and if it is awarded at 30 sheets, (not considering the frisbee) is fine.

If the larger type is more than 30 sheets, it is still cheaper! And the more you burn the more Li disturbs, the cheaper it is to engrave yourself!

If o'DAC is ACO'= AOB (two lines parallel with equal inner wrong angles) because o'= aob so o'=∠aco'

1).19,000 (divided by) (1+15%) billion) A: In 2006, the power generation was about 100 million kWh.

2).A: Yes. The 15% in question 1 is a divisor, not an exact value.

3).According to the title:

19000+m)×4%=19000+19000×13/20m760+

m=764750

19000 + 764750) 4% = 31350 (100 million) 31350 2500 = tons).

Answer: In 2008, the amount of coal used to reduce electricity consumption was 3,135 billion kWh, and the maximum amount of coal consumption could be reduced to tons.

A total of x meters between AB rooms.

x/（40+10）+（x-500）/（40-10）=42x=1100

A: The distance between the two scenic spots A and B is 1100 meters.

Last year, Sneaker A sold x pairs, and Sneaker B sold Y pairs.

x+y=12200

x(1+6%)+y(1-5%)-12200=50 can be used to get what x y is.

Hope it helps

Solution: First, deform the original equation:

2（ax-1）=3x+b

2ax-2=3x+b

2a-3)x=b+2

1) When a is not equal to 3 2, there is a unique solution: x=(b+2) (2a-3) trillion line 2) When a is equal to 3 2, and b is equal to modulus-2, there are an infinite number of solutions, because the family code is true, no matter what value x takes.

3) When a = 3 2, but b is not equal to -2, there is no solution, because no matter what value x takes, the equation cannot be true.

Hi sees that the equation has to be merged first with the same term (unknown) in Lusheng, and in this problem there is no masking x

As follows. 2（ax-1）=3x+b

2ax-2=3x+b

2a-3)x=b+2

x=(b+2)/(2a-3)

Refer to 2), a is not equal to, and when b is any number, there is only one solution to the equation.

2a-3=0,a=，b

time, countless solutions.

a=. b is not equal to -2, and there is no solution for accompanying the old man.

If you think about it again, you should be able to understand it thoroughly.

There are objections on 1) and 3). As follows.

Refer to 2), a is not equal to, and when b is any number, there is only one solution to the equation.

2a-3=0,a=，b

time, countless solutions.

a=. b is not equal to the old rule -2, there is no waiter.