1, bring 200 kilometers of water into the city. This task was handed over to two construction teams, A and B, with a construction period of 50 days. After 30 days of cooperation between the two teams, team B had to leave for 10 days because of other tasks, so team A accelerated its speed and repaired 0.6 kilometers more every day. In order to ensure the construction period, team B 10 will come back in 0 days. Q: How many kilometers did Team A and Team B originally plan to build?

Solution: Let's assume that the original speeds of Party A and Party B are A km and B km per day respectively.

According to the meaning of the question

(a+b)×50=200( 1)

10×(a+0.6)+40a+30b+ 10×(b+0.4)= 200(2)

simplify

a+b=4(3)

a+0.6+4a+3b+b+0.4=20

5a+4b= 19(4)

(4)-(3)×4

A =19-4× 4 = 3km.

B = 4-3 = 1 km

A repairs 3 kilometers every day, and B repairs 1 kilometer every day.

A It was originally planned to build 3× 50 = 150km.

B 1× 50 = 50km as originally planned.

2. Xiaohua bought four mechanical pencil and two pens, and paid 14 yuan; Xiaolan bought the same 1 mechanical pencil and two pens, and paid 1 1 yuan. Find the unit price of mechanical pencil and pen.

Solution: Suppose mechanical pencil has a pen with X yuan and a pen with Y yuan.

4X+2Y= 14

X+2Y= 1 1

The solution is X= 1.

Y=5

In mechanical pencil, the unit price is 1 yuan.

Pen unit price 5 yuan

3. According to statistics, in 2009, the profit rate of commercial housing sold by builders in a certain area was 25%.

(1) What is the cost of a commercial house with a total selling price of 600,000 yuan in this region in 2009?

(2) In the first quarter of 20 1 0, the price per square meter of commercial housing in this area increased by 2 yuan, and the cost per square meter only increased by1yuan, so the area of commercial housing that can be purchased for 600,000 yuan decreased by 20 square meters compared with 2009, and the profit rate of builders reached one third, thus seeking the profit per square meter of commercial housing sold by builders in this area in 20 10.

Solution: (1) Cost = 600/(1+25%) = 480,000 yuan.

(2) In 2000, we set the price at 2,065,438+600,000 yuan to buy B square meters.

Cost of commercial housing in 20 10 year = 60/(1+1/3) = 450,000.

60/b-2a=60/(b+20)( 1)

45/b-a=48/(b+20)(2)

(2)×2-( 1)

30/b=36/(b+20)

5b+ 100=6b

B= 100 m2

The house price per square meter in 20 10 year =600000/ 100=6000 yuan.

Profit = 6000-6000/(1+1/3) =1500 yuan.