Question

If a marble is randomly chosen from a bag that con- tains exactly 8 red marbles, 6 blue marbles, and 6 white marbles, what is the probability that the marble will NOT be white? F. \(\frac{3}{4}\) G. \(\frac{3}{5}\) H. \(\frac{4}{5}\) J. \(\frac{3}{10}\) K. \(\frac{7}{10}\)

Short answer

Answer: \(\frac{7}{10}\)

Step-by-step solution

Find the total number of marbles

To find the total number of marbles, we add the number of red, blue, and white marbles: 8 red + 6 blue + 6 white = 20 marbles.

Find the number of non-white marbles

We need to count the marbles that are NOT white. Since there are 8 red marbles and 6 blue marbles, the number of non-white marbles is 8 + 6 = 14.

Calculate the probability that the marble will not be white

To find the probability, we need to divide the number of non-white marbles by the total number of marbles: \(\frac{14 \text{ (non-white marbles)}}{20 \text{ (total marbles)}}\).

Simplify the fraction

To simplify the fraction, we find the greatest common divisor of 14 and 20, which is 2: \(\frac{14}{20} = \frac{14\div2}{20\div2} = \frac{7}{10}\). The probability that the marble will NOT be white is \(\frac{7}{10}\), which corresponds to answer choice K.

Key concepts

Mathematical Probability

Mathematical probability is the measure of how likely an event is to occur out of the number of possible outcomes. It's rooted in the concept of randomness and is quantified as a number between 0 and 1, inclusive. A probability of 0 means an event will never occur, while a probability of 1 means it will always occur.

To calculate the probability of a single event, you can use the formula:
\[\begin{equation}Probability = \frac{\text{Number of favorable outcomes}}{\text{Total number of possible outcomes}}\end{equation}\]
Understanding this fundamental concept is the first step towards solving probability problems. It's important to clearly identify the 'favorable outcomes' (what we're looking for) and the 'possible outcomes' (the entire range of outcomes that can occur).

Probability Problem-Solving

In probability problem-solving, the approach is systematic and often involves a series of steps similar to those seen in the marble exercise. Let’s look through these steps a bit more:

• Step 1: Define the problem. Determine exactly what you are trying to solve. This involves identifying the event of interest.
• Step 2: Gather information. Calculate the total number of possible outcomes and note the number of favorable outcomes.
• Step 3: Perform calculations. Use probability formulas to calculate the probability based on the information you gathered.
• Step 4: Simplify your answer. Often, you'll need to simplify fractions to their lowest terms for the final probability.

Knowing these steps and applying them to various scenarios can significantly improve your ability to solve probability problems. Remember also to consider complement events (like NOT picking a white marble), which can sometimes simplify the problem.

Probability Examples

Probability can be applied to a wide range of examples, from simple to complex scenarios. In the case of the exercise provided, picking a marble from a bag is a common example used to illustrate basic concepts of probability. Here are some additional examples to help deepen your understanding:

• Coin Toss: When you flip a fair coin, there are two possible outcomes: heads or tails. Each has a probability of \(\frac{1}{2}\).
• Rolling Dice: When rolling a standard six-sided die, each face (numbered 1 through 6) has a probability of \(\frac{1}{6}\) of appearing face up.
• Drawing Cards: If you draw a card from a standard deck of 52 cards, the chance of drawing a spade would be \(\frac{13}{52} = \frac{1}{4}\), since there are 13 spades in the deck.

Each example shows how various factors — the total number of outcomes and the number of favorable outcomes — play a crucial role in determining the probability of an event. As you encounter more complex problems, you can build upon these fundamental principles to analyze situations with greater numbers of variables and outcomes.