How many hands will you shake in a room with 20 people?

When there are 20 people in a room and each person shakes hands with every other person, we need to calculate the total number of handshakes that will occur. The formula to determine this is N - 1, where N represents the total number of people in the room.

In this case, with 20 people in the room, subtracting one from the total gives us 19 handshakes. This is because each person will shake hands with everyone else in the room, except themselves. Therefore, you would shake hands with 19 other people.

This concept of handshakes in a room with a specific number of people is a common problem in combinatorics, which is a branch of mathematics that deals with counting combinations and arrangements of sets of items. It is a simple yet interesting way to understand permutations and combinations.

It is worth noting that in today's world, with various personal comfort levels and global changes, physical contact like handshakes may not always be the preferred form of greeting. Alternative greetings such as a small wave, nod, or a smile can be equally effective and respectful.