Which piece of information given in the alternatives will additionally be required to answer the following question?
Question:
The ages of three friends A, B, and C are the ratio of 5 ∶ 4 ∶ 3. What is the age of the oldest person?

Correct option is C

Option Analysis:

• A. A is older than both B and C
  This information is already given by the ratio 5:4:3, where A is associated with the highest number (5), meaning A is indeed older than both B and C. This option does not provide any new information.

• B. A's age is an absolute multiple of 5
  This information suggests that A's age is a multiple of 5, but the ratio alone (5:4:3) does not require us to know A's absolute age. We only need to know the relative ages to answer the question. This option doesn't impact the determination of the oldest person.

• C. B was 5 years old when C was born
  This is crucial. If we know the exact age difference between B and C (since B was 5 years old when C was born), we can calculate their exact ages. This condition allows us to solve for the actual ages of A, B, and C, based on the given ratio and this extra information. This piece of information is required to determine the exact age of the oldest person.

• D. The difference between the ages of A and B is the same as the difference between the ages of B and C
  This option would give us an additional relationship between the ages of A, B, and C, but it is not necessary to determine the oldest person directly. We can still infer the oldest person from the ratio.

Conclusion:

To definitively determine the ages, Option C provides the essential piece of information needed, as it allows us to calculate the exact ages based on the age difference between B and C.

Correct Answer: C. B was 5 years old when C was born.