Question

Every living person has shaken hands
with a certain number of other persons.
Prove that count of number of people
who have shaken hands an odd number of
times must yield an even number.

Answer 1

Every living person has shaken hands

with a certain number of other persons.

Prove that count of number of people

who have shaken hands an odd number of

times must yield an even number.

Step-by-step explanation:

Every handshake  will involve 2 people. If the jth person shakes hands nj times, then the sum  of the nj must be even. If there is an odd number of odd nj then the sum will be odd.