Probability and Combinations with Marbles

The video tutorial explains how to calculate the probability of drawing two red marbles from a jar containing 15 red and 18 blue marbles. It presents two methods: using conditional probability and combinations. The first method involves calculating the probability of drawing one red marble and then another without replacement. The second method uses combinations to determine the probability of drawing two red marbles at once. Both methods yield the same result, demonstrating different approaches to solving probability problems.

What is the total number of marbles in the jar?

• 33

• 30

• 18

• 15

How do we calculate the probability of the first marble being red?

• 15/18

• 18/33

• 15/33

• 18/15

What is the probability of the second marble being red given the first is red?

• 18/33

• 14/33

• 14/32

• 15/33

What is the simplified fraction of the probability that both marbles are red?

• 5/16 x 7/15

• 5/11 x 7/15

• 5/16 x 7/11

• 5/11 x 7/16

What is the decimal approximation of the probability that both marbles are red?

• 0.1998

• 0.1899

• 0.1889

• 0.1989

What is the percentage representation of the probability that both marbles are red?

• 19.98%

• 18.89%

• 19.89%

• 18.99%

What is the total number of ways to select two marbles from the jar?

• 30 choose 2

• 33 choose 2

• 18 choose 2

• 15 choose 2

How do we express the probability of selecting two red marbles using combinations?

• 18 choose 2 / 33 choose 2

• 15 choose 2 / 33 choose 2

• 15 choose 2 / 18 choose 2

• 18 choose 2 / 15 choose 2

What is the result of the combination calculation for selecting two red marbles?

• 35/176

• 30/176

• 30/180

• 35/180

What should you do if you haven't learned about combinations?

• Use a calculator

• Guess the answer

• Skip the problem

• Use the first method