How many even numbers are there between?

How many even numbers are there between 66 and 71 ?

MetroEye: 'between' means excluding start and end numbers. Number of integers between  N1 and N2  will be  N2-N1-1

If the start number is odd and end number is even (vice versa) then the count of in between numbers will be even.

If the start and end numbers are even (or odd) then the count of in between numbers will be odd, giving the 'other' one more than the start and end type

Eg : 66  & 70  , There are 3 numbers in between ; 1 even and 2 odd.
        67 & 71  , there are  3 numbers in between ; 1 odd and 2 even.

Here 71-66-1 = 4.

So four numbers in between. 2 of them odd and 2 of them even.

There are 2 even numbers between 66 and 71.