6 people meet for a business lunch. Each person shakes hands once with

Question

6 people meet for a business lunch. Each person shakes hands once with each other person present. How many handshakes take place?

A. 30 
B. 21 
C. 18 
D. 15 
E. 10

Divyadisha · Accepted Answer

Let's look at the logic.

Every person shakes hand with other '5'. So, 6 people shake hands with 6X5= 30 people

But in this 30 we have counted two times the total handshakes (A shakes hand with B and B shakes hand with A)

So just divide 30/2= 15 total handshakes

HungNguyen · Answer

Hi
the formula to count handshakes is  \frac{n(n-1)}{2} 
Where n is the number of people

=> 6(6-1)/2 = 6*5/2 = 30/2 = 15 
=> the answer is D(15)

Here why:
if there are 2 people at the business lunch
=> the number of handshakes will be 1 (obviously)

people | handshakes
 2 | 1
 3 | 3
 4 | 6
=> we can see

2 people = 1 handshakes
3 people = 2 + 1 handshakes
4 people = 3 + 2 +1 handshakes
5 people = 4 + 3 + 2 + 1 handshakes
6 people = 5 + 4 + 3 + 2 +1 handshakes

=> the formula will be  \frac{n(n-1)}{2}

ravisinghal · Answer

Its a combination problem :-

Out of 6 we just need 2 ..order doesn't matter

6c2 = 15

Thanks

CEdward · Answer

Too trigger happy and clicked A.

A B C D E F
A shakes hands with 5
B shakes hands with 4
C ...3
D ...2
E ... 1

5 + 4 + 3 + 2 + 1 = 15

Answer is D.

USMAN098 · Answer

In a class of 78 students 41 are taking French, 22 are taking German. Of the students 
taking French or German, 9 are taking both courses. How many students are not enrolled in 
either course?

Bunuel · Answer

This question is discussed here: https://gmatclub.com/forum/in-a-class-o ... 95605.html Hope this helps.

6 people meet for a business lunch. Each person shakes hands once with

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