Elementary school mathematics can be solved by setting xy as an unknown number. There is such an exercise in the knowledge of the sixth grade scale.

For example, the plan of a rectangular playground has a scale of 1: 1 000. Measured from the map, it is 25cm long and1.8cm wide. What is the actual length and width of this playground?

Solution: Let the actual length be x meters and the actual width be y meters.

25cm = 0.25m， 18cm = 0. 18m。

0.25:x= 1: 1000

0. 18:y = 1: 1000

Then find the solutions of the two equations.