1. solution: let the car speed be x, the motorcycle speed be y, and the motorcycle travel be z hours.

4x = 6y

x = 3/2y；

6x =(z-6)y；

will

X=3/2y brings z =15;

8+ 15=23

The motorcycle arrives at Station A at eleven o'clock in the evening.

2. Solution: Assume that the number of girls in grade six is X, the number of boys in grade five is Y, the number of girls in grade five is A, and the number of boys in grade six is B.

x = 3y…… 1；

a = 2b……2；

x = 2.5a……3；

pass by

1, 2,3 finishing can get y = 5/6a；; y = 5/3b； x=5/2a

And because x, y, a and b are all positive integers.

So take a=6, y=5, b=3, x= 15.

6+5+3+ 15=29

So there are at least 29 people on the dance team.