A box contains 35 gems, of which 10 are real diamonds and 25 are fake diamonds. Gems are randomly taken out of the box, one at a time without replacement. What is the probability that exactly 2 fakes are selected?

Respuesta :

Answer:

[tex]Probability = 0.504[/tex]

Step-by-step explanation:

Given

[tex]Gems= 35[/tex]

[tex]Real = 10[/tex]

[tex]Fake = 25[/tex]

Required

Determine the probability of selecting two fakes

The probability can be represented as thus: [tex]P(Fake\ and\ Fake)[/tex]

Using the following probability formula, we have:

[tex]P(Fake\ and\ Fake) = P(Fake) * P(Fake)[/tex]

Each probability is calculated by dividing number of fakes by total number of gems:

[tex]P(Fake\ and\ Fake) = \frac{25}{35} * \frac{25-1}{35-1}[/tex]

The minus 1 (-1) represent the numbers of fake and total gems left after the first selection

[tex]P(Fake\ and\ Fake) = \frac{25}{35} * \frac{24}{34}[/tex]

[tex]P(Fake\ and\ Fake) = \frac{5}{7} * \frac{12}{17}[/tex]

[tex]P(Fake\ and\ Fake) = \frac{60}{119}[/tex]

[tex]P(Fake\ and\ Fake) = 0.504[/tex]

Hence, the required probability is approximately 0.504