Question

If a box contains 3 black, 4 red, and 5 white marbles and one is chosen at random, what is the probability it will be red?

Answer 1

To find the probability of drawing a red marble from the box, we first need to determine the total number of marbles in the box.

The total number of marbles is calculated as follows:
- Black marbles: 3
- Red marbles: 4
- White marbles: 5

Now, add these values together:
\[
3 + 4 + 5 = 12
\]

So, there are 12 marbles in total.

Next, we focus on the number of favorable outcomes, which is the number of red marbles. There are 4 red marbles.

The probability of drawing a red marble is given by the formula:
\[
P(\text{red}) = \frac{\text{Number of red marbles}}{\text{Total number of marbles}} = \frac{4}{12}
\]

Now, simplify the fraction:
\[
\frac{4}{12} = \frac{1}{3}
\]

Thus, the probability of choosing a red marble is:
\[
\boxed{\frac{1}{3}}
\]