90-a+180-a =180 a = 45 degrees.
2. The strong earthquake in Sichuan touched the hearts of Huaxin's friends. Huaxin bought 200 pencils from 0.2 yuan and pens from 5 yuan with the money from 280 yuan, and gave them to the children in the disaster area. Would you please count the number of pencils and pens she bought?
If the number of pencils is x and the number of pens is 200-x, then there is 0.2x+5(200-x)=280, and the result is x= 150.
So the pencil is 150 and the pen is 50.
3. It is known that line segment AB= 12, points C, D, E and F are on AB in turn, point C is the midpoint of AD, and points E and F are the bisectors of BD, and CF=7. What is the length of AC?
Let a be 0, then b is 12, and the corresponding c is X 1 D X2 E X3 F X4.
Point C is the midpoint of AD, CX1= 0.5x2..
E and f are bisectors of BD, so E3 =12-2 (12-x2)/3 = 4+2x2/3.
f X4 = 12-( 12-X2)/3 = 8+X2/3
CF=7 means 8+X2/3-0.5X2=7, that is, X2=6 means X 1=0.5*6=3.
That is, AC=3.
On May 1 day, 2008, Hangzhou Bay Bridge, the longest sea-crossing bridge in the world, was completed and opened to traffic. After opening to traffic, the distance from Sunan A to Ningbo Port is shortened120km. It is known that the driving time will be shortened from 3: 20 to 2: 00 when the speed of transport vehicles remains unchanged. (1)A What is the distance from Hangzhou Bay Bridge to Ningbo Port? (2) If the freight transportation cost includes the transportation cost, it is known that the transportation cost of a car from A to Ningbo Port is 1.8 yuan per kilometer and the time cost is 28 yuan per hour, then what is the transportation cost of this car from A to Ningbo Port via Hangzhou Bay Bridge?
1) the distance is shortened 120km, the time is shortened by 3: 20 -2: 4/3 hours, and the vehicle speed120/(4/3) = 90km/h.
When the time of the cross-sea bridge is 2 hours, the distance is 2*90= 180km.
2) The transportation cost is 1.8* 180+28*2=380 yuan.