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