7x-4y=m-2
The solution of the equation is x = (7m- 12)/3 1, y = (9m-11)/62;
X < 0, that is, 7m- 12 < 0, m <12/7;
Y > 0, namely 9m- 1 1 > 0, m >1/9;
So11/9 < m <12/7.
The time-of-use electricity price of power supply company is divided into two periods: peak period and trough period. The peak period is 8: 00-22: 00, 14 hour. 22: 00 in the valley-8: 00 the next day, 10 hour. The flat section increased by 0.03 yuan per kWh according to the original electricity price. The valley section is 0.25 yuan lower than the original electricity price per kWh. Xiaoming's actual electricity consumption in May was 40 kWh in the flat section and 60 kWh in the valley section. The time-of-use electricity price is 42.73 yuan.
(1) What is the electricity price per kilowatt hour in Pinggu section of Xiaoming's house this month?
Set the original x yuan per kwh:
40(x+0.03)+60(x-0.25)= 42.73；
100x- 13.8=42.73
x=0.5653
The flat price per kWh =0.5653+0.03=0.5953≈0.60 yuan.
Valley electricity price per kwh = 0.5653-0.25 = 0.3153 ≈ 0.32 yuan.
(2) If the time-of-use electricity price is not used for settlement, how much electricity will Xiao Ming's family pay in May?
0.5653×(40+60)=56.53 yuan
Organize field activities for 290 people, with luggage 100. I'm going to rent eight A's and B's .. One car can carry up to 40 people, and the luggage 10. Model B can carry up to 30 people, each with 20 pieces of luggage.
(1) Set up X-rental vehicles to help us design all possible schemes.
Let a car x b car y have:
40x+30y≥290；
10x+20y≥ 100；
x+y = 8；
Positive integer ungrouping: (5, 3); (6,2)。
(2) If the rental fees of Party A and Party B are 2000 and 1800 respectively, please choose the most economical one.
Of course, it is a combination of (5, 3). A car is expensive, the less you allow, the better.
Xiaobai went out to play with his classmates and parents, and now he is buying tickets.
Adult 35 yuan. Half price for students and adults, and 60% discount for groups (16 or more, including 16). Went to 12 people, * * needed 350 yuan.
1) How many adults and students did you go to?
I didn't buy a group ticket, so I set up Lord X:
35x+35x (12-x) ÷ 2 = 350, x=8, which means 8 adults and 4 children.
2) Which method is more economical?
It is more economical to buy 16 group tickets directly and spend 35× 16×0.6=336 yuan < 350 yuan.
The planned construction area of a market is 2400㎡. There are 80 A-type and B-type stores ... The average area of A-type stores is 28m2, and the monthly rent is 400. The average area of Class B stores is 20m2, and the monthly rent is 360. The construction area of all stores shall not be less than 80% and not more than 85% of the total area.
1) Try to determine the number of A stores.
a+B = 80；
2400×0.8≤28A+20B≤2400×0.85
The solution is 40≤A≤55, that is, shop A is in between.
2) The management department understands that the occupancy rate of Store A is 75% and that of Store B is 90%. How many A stores should be built to make the monthly rental fee W the highest?
A Average actual rental income per room = 400× 0.75 = 300; B Average actual rental income per room = 360× 0.9 = 324;
That is, the actual rental income of Class B shops is higher, that is, there are as many B as possible and as few A as possible, that is, A takes the minimum allowable value of 40.
Maximum income = 40× 300+40× 324 = 24,960 yuan.