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%

4x and 6y

im not sure though

rick has $1400 and sally has $1500

step-by-step explanation:

to find amount of money rick has after 10 years :

principal = $1000 , time = 10 years , rate = 4% annually

to find amount of money sally has after 10 years :

her friend gives to pay her $50 per year, therefore money she has after 10 years = 50 × 10 = $500

also, sally gets $1000 after 10 years,

therefore, total amount of money sally has after 10 years = 500 + 1000 = $1500

so, after 10 years : rick has $1400 and sally has $1500