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A stack of 30 science flashcards includes a review card for each of the following 10 insects, 8 trees, 8 flowers and 4 birds. What is the probability of randomly selecting an insect and then a tree???

Sagot :

The probability (P) of event A occurring is:

[tex]P(A)=\frac{\text{ number of favorable outcomes to A}}{\text{ total number of outcomes}}[/tex]

The probability of 2 consecutive events A and B occur is:

[tex]P=P(A)*P(B)[/tex]

Then, let's calculate the probability of selecting an insect:

Favorable outcomes: 10

Total outcomes: 30

[tex]P(insect)=\frac{10}{30}=\frac{1}{3}[/tex]

Now, let's calculate the probability of selecting tree:

If the insect card is replaced:

Favorable outcomes: 8

Total outcomes: 30

[tex]P(B)=\frac{8}{30}=\frac{4}{15}[/tex]

If the insect card is not replaced:

Favorable outcomes: 8

Total outcomes: 29

[tex]P(B)=\frac{8}{29}[/tex]

The probability of randomly selecting an insect and then a tree is:

With replacement:

[tex]\begin{gathered} P=\frac{1}{3}*\frac{4}{15} \\ P=\frac{4}{45} \end{gathered}[/tex]

Without replacement:

[tex]\begin{gathered} P=\frac{1}{3}*\frac{8}{29} \\ P=\frac{8}{87} \end{gathered}[/tex]

Answer:

With replacement: 4/45

Without replacement: 8/87