As the picture shows, Xiaoli drew a plan with the school as the observation point. (1) Change the line scale of this drawing to the digital scale of _ _ _ _. (2)

Then1cm: 20000 cm =1:20000;

(2) Sheng Yuan Hotel is located 30 northwest of the school, and the bus stop is 50 southwest of the school.

The distance between the school and Shengyuan Hotel is 2 cm.

Then the actual distance from the school to Sheng Yuan Hotel is: 2 ÷120000 = 40000 (cm) = 400 (m);

The distance between the school and the bus station is 3 cm.

Then the actual distance from the school to the bus stop is: 3 ÷120000 = 60000 (cm) = 600 (m);

(3) Because 400 meters = 40,000 centimeters,

The distance from Chinese medicine hospital to post office is: 40000×120000 = 2 (cm);

As shown in the picture, it is the location of Chinese medicine hospital:

(4) The distance from the school to the post office is 1cm.

The actual distance from the school to the post office is:1÷120000 = 20000 (cm) = 200 (m);

So Xiaoli needs the following time:

(600+200+400)÷50,

= 1200÷50,

=24 (minutes);

A: Xiaoli walks at a speed of 50 meters per minute, and it takes about 24 minutes from the bus station to the school, post office and Chinese medicine hospital.

So the answer is: (1)1:20000; (2) 30,400 in the north and west and 50,600 in the south and west; (4)24.