A number from 1 to 10 is chosen at random. What is the probability of choosing a 5 or an even number?

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hala718's profile pic

hala718 | High School Teacher | (Level 1) Educator Emeritus

Posted on

The numebers chosen are from 1 to 10.

Then possible outcomes are: 1,2,3,4,5,6,7,8,9,10

The probability of chosen a 5  OR and even number = probability of chosen a 5  + probability of chosen an even number.

Let us calculate each event:

P ( 5) = 1/10

Even number are: 2,4,6,8,10

==> P(even) = 5/10

Then :

P( 5 OR even) = P(5) + P(even)

                       = 1/10 + 5/10 = 6/10

                       = 3/5

==> P ( 5 or even) = 3/5

neela's profile pic

neela | High School Teacher | (Level 3) Valedictorian

Posted on

We can chose randomly  a number from 1 to 10 in 10 ways, as any of the number in a random choice is equally likely.

Number of ways of getting particular number 5 in a random choice of numbers from 1 to 10 is only one  way.

The number of ways of getting an even number  (evens are 2,4, 6,8 and 10) = 5 ways.

Therefore the probablity of getting a 5 or an even number in a choice = number ways of getiing 5 or an even number / total number of ways of chosing any number = (1+5)/10 = 0.6.

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