If there are 42 people, they each shake hands once with everyone else, how many hand shakes are there?

Answer 1

To say the answer is 1722 is to count some handshakes twice. When person A shakes with person B, and then again when person B shakes with person A. <<<****The correct answer is 861 shakes.****>>> Person A shakes with 41 people and then he's out. Because he's shaken with everything. So there is 41 shakes so far. Then person B shakes with everyone left, totaling 40 shakes, then he's out. Then person C shakes with 39 people and so forth. The answer given stating 41+40+39+38... is the correct formula. Simplified is 41 times 21. This formula is found by adding the first and last number (0 if there is an odd number and the first number is 1). By adding the number one less than the first number and the number one more than the last number will always yield the same results. So now multiply by the number of time you would add 2 numbers together to get this same result. Well 1 through 41 equals 41 numbers. Plus 0 is 42 numbers. So if you have 42 numbers and only use each number once and add 2 numbers at a time, then Divide 42 by 2 to find how many times you would add 2 numbers together to get 41.... and you get 21.

Answer 2

861 shakes...... i got this by adding 41+40+39,etc. Once person A has shook hands with person B, person B can't shake hands again with Person A. So that's why the number goes down each time.

Answer 3

1764 handshakes-42 multiplied by 42

Answer 4

That would be 1764 hand shakes. Wow. Think of all the germs being passed around. Hope they have their hand cleanser!

Answer 5

1764

Answer 6

1722 is the answer they each shake hands with 41 other people.
42*41 = 1722.

Answer 7

There will be 903 hand shakes.
Here is how i got 903.

42+41+40+39 ect. Until you get to 1 or 0.

Answer 8

861

Answer 9

Alot

Answer 10

1764.