A bag has 10 mmarbles, and 7 are black. Petra picks 2 marbles without replacing the first. What is the probability that both are black?

The probability that Petra picks two black marbles, without replacing the first one is 7/15 or 46.7%.

Step-by-step explanation:

Let's recall the formula of the probability:

Probability = Number of favorable outcomes/Total number of possible outcomes,

therefore, the probability of picking a first black marble is:

P = 7/10

now, let's find out the probability for picking a second black marble:

P = 6/9

It's different than the first one because Petra did not replace the first one.

Now, the probability that both are black is:

P = 7/10 * 6/9

P = 42/90 = 7/15

The probability that Petra picks two black marbles, without replacing the first one is 7/15 or 46.7%

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investment b is an ordinary annuity with $3,909.64 in the account after one year.

step-by-step explanation: