"Hand Shake Problem" is a very common question in many competitive exams such as CSIR in the Aptitude part questions. Here we are discussing a simple formula for answering this question.

Watch this two minute video or refer the questions below

**Practice Problems**

1. In a group of 11 persons, each shakes hand with every
other once and only once. What is the total number of such handshakes? (CSIR DEC, 2018)

This is the formula

**Answer:**Total No of hand shakes (T)=

**n(n-1)/2**

No
of persons n=11

N=11 (11-1)/2

=11x10/2=110/2

**Answer: 55 handshakes****2. If there are 10 football teams in a tournament, how many games must be played in order for each team to play every other team exactly once? (same pattern question in a different context)**

**Answer:**No of games=

**n(n-1)/2**

N=10 (10-1)/2

=10x9/2=90/2

**=45 games****Use this formula for answering any questions of this pattern**

**Thank you so much and best wishes for your exam**

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