1. From the departure to the first meeting, they walked a whole journey together. Their time is equal and the distance ratio is equal to the speed ratio.

The speed ratio of Party A and Party B is 4: 3, so the distance ratio is 4; 3 (the number of copies in the whole process is 3+4=7)

After the encounter, the speed of A is 4*( 1+ 10%)=4.4 B, and the speed of A is 3*( 1-20%)=2.4. After meeting, the two continued to walk together for a while.

A arrives at B, and B arrives at a distance of 26 kilometers ... The distance of peers is 26 kilometers less than the whole journey. Reuse time is fixed,

Speed ratio and distance ratio. The speed ratio of the two cars is 4.4: 2.4 =11:6, and the distance traveled by A is equivalent to the distance traveled by B before meeting. Then the 6-minute distance traveled after B meets is equivalent to the original distance of 3/11* 6 =18/1.

26/(4-18/11) =11km (each distance). The seven distances of the whole journey are 1 1*7=77 km.

2. The total number of the two grades is 2+3=5, and the average height of the two grades is 1.54m, so the total height of the two grades is

1.54*5=7.7 meters. Similarly, the total height of grade five students is 1.45*2=2.9 meters. This can get the total height of the sixth grade students.

So the average height of the sixth grade is

(7.7-2.9)/3 = 1.6m