Last weekend, the number of visitors at a zoo was z. This weekend, the number of visitors at the zoo can be represented by the given expression.

Which set of statements is true?
A.
The number of visitors at the zoo increased by 113%.
An equivalent expression that represents this situation is z + 1.13z.
B.
The number of visitors at the zoo increased by 13%.
An equivalent expression that represents this situation is z + 0.13z.
C.
The number of visitors at the zoo decreased by 113%.
An equivalent expression that represents this situation is z − 1.13z.
D.
The number of visitors at the zoo decreased by 13%.
An equivalent expression that represents this situation is z − 0.13z.
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1 answer

Let's analyze each option systematically in relation to the percentage change.

  1. Option A:

    • Claim: The number of visitors at the zoo increased by 113%.
    • Expression: \( z + 1.13z \)
    • Evaluation: An increase of 113% means the new visitors would be the original plus an additional 113% of the original, which is \( z + 1.13z = 2.13z \). This indicates a total of 213% of the original number of visitors, which is not a typical increase and doesn't align with the percentage described. This statement is false.
  2. Option B:

    • Claim: The number of visitors at the zoo increased by 13%.
    • Expression: \( z + 0.13z \)
    • Evaluation: An increase of 13% means the new visitors would be the original plus an additional 13% of the original: \( z + 0.13z = 1.13z \), representing a total of 113% of the original number of visitors, which correctly reflects a 13% increase. This statement is true.
  3. Option C:

    • Claim: The number of visitors at the zoo decreased by 113%.
    • Expression: \( z - 1.13z \)
    • Evaluation: A decrease of 113% is nonsensical, as it implies a reduction beyond the total number of visitors. The expression would result in a negative number of visitors (specifically, \(-0.13z\)), which does not apply here. This statement is false.
  4. Option D:

    • Claim: The number of visitors at the zoo decreased by 13%.
    • Expression: \( z - 0.13z \)
    • Evaluation: A decrease of 13% means that the new visitors would be \( z - 0.13z = 0.87z \). This indicates that the number of visitors was 87% of the original, which accurately reflects a 13% decrease. This statement is true.

Conclusion:

The true statements are:

  • B: The number of visitors at the zoo increased by 13%. An equivalent expression that represents this situation is \( z + 0.13z \).
  • D: The number of visitors at the zoo decreased by 13%. An equivalent expression that represents this situation is \( z - 0.13z \).

These two statements are true, while A and C are false.