By Bill Rowe http://forums.wolfram.com/mathgroup/archive/2004/Apr/msg00357.html
In[1]:= Timing[For[sum = 0; n = 1, n < 100001, n++, sum += n]] Out[1]= {1.2999999999999998*Second, Null} In[2]:= Timing[Plus @@ Range[10000]] Out[2]= {0.009999999999999787*Second, 50005000}