Junior high school math application problems good extra points, can be detailed is the master .

Solution: If it takes X days for A to complete alone, then it takes (X-20) days for B to complete alone.

by the title. 8+960 x=960 (x-20)x=60 If A is done alone, the total cost is.

If B is done alone. The total cost is:

If A and B cooperate.

It takes 960 (16+24) = 24 days to complete. The total cost is:

Therefore, the cooperation between A and B is the most cost-effective.

Premise: The processing fee paid by the company for the production of the product is certain.

Therefore, the processing fee for each product is 5 yuan.

A produces 16 pieces per day and B produces 24 pieces per day.

2) In addition to paying a fixed processing fee, the company is the key to deciding how much to pay, assuming that the two factories jointly complete the subsidy, and the subsidy should be two.

The subsidy expenditure is 240 yuan and the construction period is 24 days.

Assuming that it is completed by a factory alone, because B's processing time is short, B should complete the subsidy expenditure of 200 yuan and the construction period is 40 days.

Comprehensive consideration (200 + 240 + 40 + 24) 2 = 252 when the subsidy expenditure is 220 yuan, the construction period is 32 days.

So the total expenditure is:

960 * 5 + 220 = 5020 yuan.

The total construction period is 32 days.

If the time of cooperation between the two factories is t, then the time of B alone is 32-t40t+24(32-t)=960

t=12, that is, the two factories cooperate for 12 days, and the B factory works alone for 20 days.

Divided into two steps: 1) First, if A can process x products per day, and B can process Y products per day, then there are:

960/x=960/y+20

x+8=y;

From the above two equations, x and y can be solved; x=16,y=242) for the most cost-effective scenario:

If there are m pieces of products handed over to A for processing, the total amount of money spent is:

80m x+120(960-m) y+5[m x+(960-m) y], substituting the x and y obtained in the first step into the above agenda, it is found that the last is a primary polynomial about m:

5/48)m+5000;

From this formula, it is obvious that the smaller m, the less money is spent, the minimum value of m is 0, and the smaller m is, it means that B processes more and the faster the speed, so m=0 is the best solution: the least money, the shortest time. That is, all products are processed by B.

Same question you asked.

If the requirement is to have no less than 10 vehicles for each of the three types of watermelons:

Let the number of cars shipping A and B be X and Y respectively, then 4X+5Y+6(40-X-Y)=200, simplified to 2X+Y=40, and 40-X-Y is not less than 10, and X+Y is not greater than 30, (1) The number of cars A, B, and C can be ., respectively

2) 1600*4x+1000*5y+1200*6(40-x-y)>250000, then 4x+11y<190, the value of (1) can be narrowed to this one.

÷80=3200

Therefore, the per capita consumption is 3,200 yuan.

2. Set an increase of x per capita

then the number of people increases, and the total income increases.

So 25600 (1+

1+x>0

So x = so the total revenue is 100 million yuan.

Solution: Let each selling price be x yuan, and the daily profit will be y yuan

If x 18, the sales volume is 60-5 (x-18), and each profit is (x-10) yuan, then the daily profit is y=[60-5(x-18)](x-10)=-5(x-20) 2+500, at this time, when the selling price is set at 20 yuan each, the profit is the largest, and the maximum profit is 500 yuan;

If x 18, the sales volume is 60 + 10 (18-x), and each profit is (x-10) yuan, then the daily profit is y = [60 + 10 (18-x)] (x-10) = -10 (x-17) 2 + 490, at this time, when the selling price is set at 17 yuan each, the profit is the largest, and the maximum profit is 490 yuan;

Therefore, when the price of each product is set at 20 yuan, the daily profit is the largest

When the price is raised, the price is increased by x.

then each net profit (18+x-10) yuan, sell (60-5x).

Net income (18+x-10) (60-5x) yuan.

Net income (8+x) (60-5x) yuan, net income 480-5x +20x yuan.

To make (-5x +20x) as large as possible, make -5(x -4x) = as large as possible.

5(x -4x)=-5(x -4x+4)+20=-5(x-2) +20<=20, the maximum value of this formula is 20

The maximum net profit is $500 (priced at $20).

When the price is lowered, it is set to be reduced by Y yuan.

then the net income (8-y) (60 + 10y) yuan, the net profit is 480 + 20y-10y yuan.

Then make 20y-10y as large as possible, 20y-10y = -10(y-1) + 10< = 10 yuan, and the maximum of the original formula is 10 + 480 = 490 yuan (that is, the price is reduced by 1 yuan).

490, <500, it should be priced at 20 yuan.

Downstairs [60-5 (x-18)] means: when the price is x yuan, you can sell a few pieces.

Explanation: How much money does a piece make a net profit (x-18) means a few dollars up, according to the title, a piece of less than 5 pieces, it will sell 5 (x-18) pieces less, the original sale of 60 pieces, now sell [60-5 (x-18)] pieces, x-10) means how much money a piece of net income, the downstairs calculation method means that when each selling price is x yuan, a few dollars will be netted, so as to find the max net income.

Thanks, I'm tired.

Let the profit be y and the unit price be x; then y=(x-10)(60+(18-x)*10),(x<=18); y=(x-10)(60-(18-x)*5),(x>18);Solve this piecewise function

See for yourself the answers. What are you asking here?

If the current express train is x kilometers per hour, the maglev train will be 175 per hour

x=125125 multiplied by.

A: Maglev trains are kilometers per hour.

Let the speed of the magnetic levitation be x, then the velocity of the magnetic levitation is, (200 x)-(175, find x, then the velocity of the magnetic levitation can be obtained.

Solution: If the current express train is x kilometers per hour, the maglev train is 175 per hour

x=125125×

A: Maglev trains are kilometers per hour.

Solution: Set a discount of x yuan per unit to increase the profit every day.

When the price of each unit is 3500 yuan, profit = (3500-2500) * 8 = 8000 Now profit = 8000 * (1 + yuan.

3500-x-2500)*[8+(x 100)*2]=9000 Calculate: x=100,500

In order to sell more refrigerators, so each unit is discounted by 500 yuan.

3500-2500-100x）*（8+2x）=(3500-2500)*8*

Calculate that there will be two solutions, round off the negative value, and what is left is the answer.

The profit when it is not preferential is (3500-2500)*8=8000 yuan.

The total profit after the increase in profit is 8000 (1+ yuan.

If the discount is x yuan for each unit, the total sales volume is (x 2)+83500-2500-x)(8+x 2)=9000 to get x=100 or x=500

Therefore, as long as each unit is discounted by 100 yuan, it is enough.

Can be verified. A discount of 100 yuan can sell 2 more units, a total of 10 units are sold, the profit of each unit is 900 yuan, and the total profit is 9000 yuan.

Solution: Set a price reduction of X yuan.

3500-2500-x）*（8+x/100 *2）/（3500-2500）*8=1+

Selling price - purchase price - price reduction for each unit profit) * (8 + increase in sales quantity is the total amount of sales) = profit per day after the price reduction (3500-2500) * 8 is the profit per day before the price reduction The growth rate is, that is to say, the profit per day after the price reduction is the profit per day before the price reduction (1 + times.)

Profit per day after the price reduction Profit per day before the price reduction = 1 + i.e. the formula of the first line.

The solution is x1=100 and x2=500

In order to sell more refrigerators, x1 = 100 rounded.

A: Each unit should be discounted 500 yuan.

Solution: Set a price reduction of X yuan.

3500-2500-x）*（8+x/100 *2）/（3500-2500）*8=1+

The growth rate is, that is, the profit per day after the price reduction is 1+ times the profit per day before the price reduction.

Profit per day after the price reduction Profit per day before the price reduction = 1+

The solution is x1=100 and x2=500

In order to sell more refrigerators, x1 = 100 rounded.

A: Each unit should be discounted 500 yuan.