Use what you have learned about mutually inclusive and exclusive events.

Apply the formula for calculating the probability of events A or B.



There are four presidential candidates in a country. A street survey was conducted asking 2,500 registered voters which candidate they will vote for in the coming election. The table summarizes the results of the survey.

Presidential Candidates Number of Supporters
Candidate 1 250
Candidate 2 1,250
Candidate 3 450
Candidate 4 550


Part 1: What is the probability of randomly selecting a person who will vote for Candidate 1 or 2?

(2 points)
Responses

2502500
250 over 2500

15002500
1500 over 2500

10002500
1000 over 2500

12502500
1250 over 2500
Question 2
Part 2: If 1,000 more voters are surveyed, how many of them will likely prefer Candidate 3 or 4? Be sure to use the NEW TOTAL amount of voters to calculate your answer. Show your work and explain your answer.(2 points)

1 answer

To find the probability of randomly selecting a person who will vote for Candidate 1 or Candidate 2, we can use the formula:

P(A or B) = P(A) + P(B) - P(A and B)

In this specific case, since Candidates 1 and 2 cannot be supported by the same voter, they are mutually exclusive. Therefore, P(A and B) = 0.

  1. Number of supporters for Candidate 1: 250
  2. Number of supporters for Candidate 2: 1,250

Now we calculate the total number of supporters for Candidates 1 and 2:

\[ \text{Total supporters for Candidate 1 or 2} = 250 + 1250 = 1500 \]

The total number of surveyed voters is 2,500.

Now, we can calculate the probability:

\[ P(\text{Candidate 1 or 2}) = \frac{\text{Total supporters for Candidate 1 or 2}}{\text{Total surveyed voters}} = \frac{1500}{2500} \]

So the answer is:

1500 over 2500.


Part 2

If an additional 1,000 voters are surveyed, the new total number of surveyed voters will be:

\[ \text{New total} = 2500 + 1000 = 3500 \]

To estimate how many voters would likely prefer Candidate 3 or Candidate 4, we can look at the survey results we have.

  • Number of supporters for Candidate 3: 450
  • Number of supporters for Candidate 4: 550

Adding these gives:

\[ \text{Total supporters for Candidate 3 or 4} = 450 + 550 = 1000 \]

Now, we calculate the proportion of voters who supported Candidates 3 and 4 based on the initial survey of 2,500 voters:

\[ \text{Proportion of Candidate 3 or 4} = \frac{1000}{2500} = 0.4 \]

Now, we can apply this proportion to the new total number of voters (3,500) to estimate how many would prefer either Candidate 3 or Candidate 4:

\[ \text{Estimated supporters for Candidate 3 or 4} = 0.4 \times 3500 = 1400 \]

Thus, if 1,000 more voters are surveyed, we can estimate that approximately 1,400 more voters will likely prefer Candidate 3 or 4.