Suppose you fill a glass with ice cubes .when the ice cubes melt, is the glass still full ?

Well, you can't "fill" the glass with ice cubes to begin with.
The ice cubes never fit together perfectly, and there are always
a lot of air-spaces between them.  When the ice melts, there is
almost exactly the same amount of air in the glass as there was
originally. (Actually, a tiny bit more, for other reasons.)

At a constant it will take one hour to travel 32 mi.at that speed it will take 1/2 hr to travel the remaining 16 mi.it will take 1+1/2 hr to travel the 48mi @ 32mph.so 1 hr = 60 min& 1/2 hr = 30 min1+1/2 hr = 90 min.there are 60s in each 90 × 60 = 3600 seconds.the real question seriously is he why are they driving so slow? ! lol.