Question

There are 9 people that have a conversation with each other exactly one time.

Answer 1

The question is an illustration of arithmetic sequence.

The number of conversation for 19 people is 171

(a) 9 people

$Total = \frac{9 \times 8}{2}$

9 represents the number of people

8 represents the number of conversation each person had

2 represents the number of people having a conversation at once (i.e 2 people at once)

(b) 19 people

We have:

$n = 19$

The number of conversation is:

$Total = \frac{n \times (n -1)}{2}$

So, we have:

$Total = \frac{19 \times (19 -1)}{2}$

$Total = \frac{19 \times 18}{2}$

$Total = 19 \times 9$

$Total = 171$

Hence, the number of conversation for 19 people is 171

Read more about arithmetic sequence at:

brainly.com/question/18109692