Question

For the following questions use the information given to find the probability. Write your answer as a fraction or with a colon in lowest terms. A jar contains 3 red, 7 orange, and 2 blue marbles.

1. If you pick one without looking, find the probability of drawing an orange marble.
2. If you pick one without looking, find the probability of drawing a red or blue marble.
3. If you pick one without looking, find the probability that the marble you draw will be neither orange nor blue.
4. You pick a red marble out of the jar without looking. If you keep the red marble in your hand and pick another marble, what is the probability that it will also be red?
5. You pick an orange marble out of the jar without looking. If you keep the orange marble in your hand and pick another marble, what is the probability that the second marble will be blue?

Answer 1

Number of red marbles = 3

Number of orange marbles = 7

Number of blue marbles = 2

total number of marbles in the jar =3+7+2 =12

If you pick one without looking,

probability of drawing an orange marble =Number of orange marbles in the jar / total number of marbles in the jar = 7/12

If you pick one without looking,

probability of drawing a red or blue marble = (Number of red marbles + Number blue marbles)/total number of marbles = (3+2)/12 = 5/12

If you pick one without looking,

the probability that the marble you draw will be neither orange nor blue i,e probability of drawing a red marble

= Number of red marbles(not orange and blue) / Total number of marbles = 3/12 =1/4

You pick a red marble out of the jar without looking. If you keep the red marble in your hand and pick another marble, the probability that it will also be red:

Since you picked a red marbles, Number of red marbles left in the jar = 3-1=2; Number of marbles left in the jar = 12-1=11

Therefore,

You pick a red marble out of the jar without looking. If you keep the red marble in your hand and pick another marble, the probability that it will also be red = 2/11

you pick an orange marble out of the jar without looking. If you keep the orange marble in your hand and pick another marble, the probability that the second marble will be blue

Since you picked a orange marble, Number of blue marbles = 2(Same as before); Number of marbles left in the jar = 12-1=11

you pick an orange marble out of the jar without looking. If you keep the orange marble in your hand and pick another marble, the probability that the second marble will be blue = 2/11