Question

Natalia is a girl in a math class with a total of 11 girls and 9 boys. If the teacher selects one student at random to go to the board, what is the probability that Natalia will be selected?

A box of pens contains a total of 28 pens. If 4 of the pens are red and the rest are blue, what is the probability that the first pen pulled from the box will be red?

Katelyn has a package of 24 jelly beans. There are 9 cherry jelly beans in the package. What is the probability that the first jelly bean Katelyn pulls out of the package will be a cherry jelly bean?

A marble is drawn at random from a bag containing 2 blue marbles, 3 yellow marbles, and 7 orange marbles. What is the probability that the marble is not yellow and not blue?


(Five Stars & Thanks to whoever answers first)

Answer 1

First, let's find how many students there are in total:

11 girls + 9 boys

= 20 students.

Out of those 20 students, we are trying to find the probability if Natalia will be selected first.

There is only one Natalia.

So, out of those students, the probability of selecting Natalia is a:

1/20 probability

(if wanted to convert into a percentage):

1/20 x 100

= 5% probability

Since we already know there are 28 given pens in total and 4 of them are red pens, there is a:

4/28 chance of selecting a red pen which can be simplified to a 1/7 probability.

(if wanted to convert into a percentage):

1/7 x 100

= 14% probability

Since we already know there are 24 jelly beans in total and 9 of them are cherry beans, there is a:

9/24 chance/probability of selecting a cherry jelly bean.

(if wanted to convert into a percentage):

9/24 x 100

= 37.5% probability

Let's first figure out how many marbles there are in total.

2 + 3 + 7

= 12 marbles in total.

Now let's exclude the marbles that are blue and yellow, leaving us with 7 orange marbles.

So the probability of selecting a marble that isn't blue/yellow is a:

7/12 probability

(if wanted to convert into a percentage)

7/12 x 100

= 58% probability