Hand Shake Problem

Puzzle Problem : (Hand Shake Problem)
Ten people (five couples) go to a party and start shaking hands.
You don't shake your spouse's hand or (of course) your own.
Give number of handshakes that happened at the party.

Answer:

 There are totally 40 handshakes....

First couple handshake with other is 8+8 = 16
Second couple handshake with other except first couple..becuase we already add their handshakes.
so i.e. 6+6 = 12
Third couple handshakes is 4+4 = 8 (minus the first two couples handshake)
Fourth couple handshakes is 2+2 = 4 (minus the first three couples handshake)
Last couple handshakes is 0+0 = 0 (minus the first four couples handshake)

so total 16+12+8+4 = 40