Question

In a group of 20 people, 5 cannot swim. If two people are selected at random, what is the probability that neither of them can swim?

Answer 1

5 people out of 20

so the possibilities of picking two people will be

CN,CN. (Cn is cannot swim & C is can)

CN,CN

CN,C

C,CN

& so on. like this totally 14 will come..

so there

only 2 possibilities that neither of them cannot swim.

so the probability is 2/14

=1/7

Answer 2

Answer:

According to the question 5 cannot swim and 15 are able to swim, and probability is nothing but ratio of no. of possible outcome to the no. of total outcomes.

According to the formula first we have to selected one person out of 20 people and again from 19 person.

So the 1st step will be 5/20 since 5 are not able to swim out of 20

And then 2nd step will be 4/19 since after selecting one person who is not able to swim there are now 4 who are not able to swim out of 19.

So the ans will be (5/20) X (4/19)

The multiplication is taken because when we are selecting person one by one( 1st person and 2nd person and so on) then we have to take multiplication sign.

= 20/380

= 1/19

Hope It Helps!

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