a Math question

lilya

Five people meet and exchange handshakes. If exactly 3 of the people each shake hands with 3 people and if 1

person shakes hand with only 1 other person, then what is the least number of handshakes that could have been

exchanged?

Ans is 6. How to think about it?

isenetlab12

if 4 persons shake each other, then (P4,2)/2=6
since another one person only shake with 1 other person, which should be included in the above 4 persons,so one of the above person must shake hands with only 2 of the 4 above persons, or it will violate the original condition.
so the least handshakes are 6+1-1=6