If a, b, c, d, e are five consecutive odd numbers, their average Is:

Solution:  
Clearly,b=a+2,c=a+4,d=a+6 and e=a+8.
Average (a + (a + 2) + (a + 4) + (a + 6) + (a + 8)) / 5 = (5a + 20) / 5
                                                                                  = (a + 4)