Question

There are “n” candies in a jar. 7 of the candies are red. The rest of the candies are blue. Kevin takes at random a candy from the jar.

He eats the candy (clue:   is this a "replacement" or "without replacement" problem?). Kevin then takes at random another candy from the jar (clue: this second candy is picked from how many total candies? less or equal to "n"?) . He eats the candy. The probability that Kevin eats 2 red candies is: ? (clue: what is the probability of 1st outcome 'red candy' & what is the probability of the 2nd  outcome 'again red candy'? Then multiple 1st probability by 2nd probability).

Design and share your own example. At the end of your example, write the specific concept you demonstrated.

Answer 1

Number of candies in the jar = n

Number of red candies = 7

Number of blue candies = n - 7

Probability of picking Red candy(P1) =

Number of red candies/ Total candies = 7/n.

After picking a candy from the jar, Kevin eats it. So this is a without replacement problem.

Number of candies in the jar = n - 1

If red candy was picked in first attempt, number of red candies left in the jar = 6

Kevin again picks up a candy from the jar.

Probability of picking 2nd red candy(P2) = 6/(n-1)

So Probability of picking 2 red candies serially = P1*P2

= (7*6)/(n*(n-1)).