19.( 1) It takes 15/60h = 15 minutes to drive the train to the examination room, 15 minutes to return the fault, and 15 minutes to send the other four people to the examination room, a * *.

(2) It takes 15min for the car to drive from the fault to the examination room, and the other four people walk to the examination room at the same time. By the time the bus arrived at the examination room, people had already walked 5/4km. At this time, it takes (15-5/4)/(15+60) =11/60h for the car to take four people to the examination room.

20.( 1) The * * distance between Party A and Party B is176-1=175km. If the speed of Party B is xkm/h, the speed of Party A is (1.5x+5) km/h. ..

( 1.5x+5)*( 10-2)+( 10.5-8)* x = 176- 1

X=30 (optimal speed)

1.5x+5=50 (one speed)

(2) If Party A completes 1/24 in half an hour, 112 will be completed within1hour. Let b complete x quantities per hour, then

( 1/ 12+x)*( 12+4- 10.5)= 1- 1/24

x= 1/ 1 1

B It takes 1 1 hour to do the whole project alone.