One morning, Sara goes out to exercise. At $$\rm 6.30$$ a.m., Sara leaves home and jogs at a speed of $$8$$ km per hour. At $$\rm 8.30 $$ a.m., she feels a little bit tired and walks at half her jogging speed. At $$\rm 9.30$$ a.m., Sara ends her exercise. How many kilometres has Sara travelled during her exercise? 
Overseas Competition->Knowledge Point->Distance Word Problems->Distance Word Problems on Straight Road Overseas Competition->Knowledge Point->Word Problem Modules