Nicole pulls a colored marble out of a bowl, choosing the marble at random. There are 120 marbles in the bowl, of which 80 are black, 28 are white, and the rest are red. Use words and numbers to describe the probability that she will pull a red marble out of the bowl. Show your work.

7th grade level

1 answer

To find the probability that Nicole will pull a red marble out of the bowl, we first need to determine how many red marbles there are in the bowl.

  1. Total Marbles in the Bowl: 120
  2. Black Marbles: 80
  3. White Marbles: 28

Now, we'll figure out how many marbles are red by subtracting the number of black and white marbles from the total number of marbles.

\[ \text{Number of Red Marbles} = \text{Total Marbles} - (\text{Black Marbles} + \text{White Marbles}) \]

Calculating the number of red marbles:

\[ \text{Number of Red Marbles} = 120 - (80 + 28) \] \[ = 120 - 108 \] \[ = 12 \]

Now that we know there are 12 red marbles, we can calculate the probability of pulling a red marble.

The formula for probability is:

\[ \text{Probability (P)} = \frac{\text{Number of favorable outcomes}}{\text{Total number of outcomes}} \]

In this case, the "favorable outcomes" represent the red marbles, and the "total outcomes" represent all the marbles in the bowl.

So, we can plug in the numbers:

\[ P(\text{Red Marble}) = \frac{\text{Number of Red Marbles}}{\text{Total Marbles}} = \frac{12}{120} \]

Now, we can simplify \(\frac{12}{120}\):

\[ P(\text{Red Marble}) = \frac{12 \div 12}{120 \div 12} = \frac{1}{10} \]

This means that the probability that Nicole will pull a red marble out of the bowl is \(\frac{1}{10}\).

Final Answer: The probability that Nicole will pull a red marble is \(\frac{1}{10}\) or 10%.