Question 144789
Distance(d) equals Rate(r) times Time(t) or d=rt;  t=d/r and r=d/t
Distance travelled in the first 30 min:
d=60*(1/2)=30 km 
Distance remaining=80-30=50 km

Now, in order to drive the total distance in 1 hour, she needs to drive the remaining 50 km in 30 min, so:

r=d/t=50 km/(1/2)=100 km/hr

Hope this helps---ptaylor