Understanding the Logic Puzzle: Friend's Ages

This question asks us to determine the youngest person among five friends (A, B, C, D, and E) based on a series of clues about their relative ages. We need to carefully analyze each piece of information and combine them to figure out the correct order of their ages from youngest to oldest.

Analyzing the Clues

Let's break down the given statements one by one:

• Clue 1: C is older than only one friend.
• Clue 2: E is older than D.
• Clue 3: Only two persons are older than D.
• Clue 4: B is older than E.

Solving the Age Order Puzzle

We have five friends, so there are five positions in the age order from youngest to oldest.

From Clue 1 ("C is older than only one friend"), we know that there is exactly one person younger than C. This places C as the second youngest person.

Let's represent the order from youngest to oldest. There are 5 slots:

\( \text{\_\_} < \text{\_\_} < \text{\_\_} < \text{\_\_} < \text{\_\_} \)

Placing C based on Clue 1:

\( \text{\_\_} < \text{C} < \text{\_\_} < \text{\_\_} < \text{\_\_} \)

From Clue 3 ("Only two persons are older than D"), we know there are exactly two people older than D. This means D is the third oldest person. In a list of five, being the third oldest means D is in the third position from the oldest end, or the third position from the youngest end.

Let's verify this: If D is third oldest, the order from oldest to youngest is: Oldest > Second Oldest > D > Fourth Oldest > Youngest. This confirms D is in the middle position.

Combining this with our previous placement of C:

\( \text{\_\_} < \text{C} < \text{D} < \text{\_\_} < \text{\_\_} \)

Now consider Clue 2 ("E is older than D") and Clue 4 ("B is older than E").

• E must be in one of the two positions older than D.
• B must be older than E, which means B must be in a position older than E.

The two remaining positions are the fourth and fifth spots (older than D). Since B is older than E, B must be in the fifth spot (oldest) and E must be in the fourth spot.

Placing E and B:

\( \text{\_\_} < \text{C} < \text{D} < \text{E} < \text{B} \)

We have now placed C, D, E, and B. The only friend left is A, and the only position left is the first spot (youngest).

Therefore, A must be the youngest person.

The complete age order from youngest to oldest is:

\( \text{A} < \text{C} < \text{D} < \text{E} < \text{B} \)

Summary of Age Order

Based on this deduction, the youngest among all the friends is A.

Revision Table: Checking the Clues

All clues are satisfied by the order A < C < D < E < B.

Additional Information: Solving Logic Puzzles

Logic puzzles like this one require careful reading and step-by-step deduction. Here are some tips:

• Read all clues first to get an overview.
• Look for clues that fix a person's position relative to a specific number of others (e.g., "older than only one", "only two older than"). These are often good starting points.
• Use symbols or diagrams (like the inequality chain \( < \)) to represent the relationships.
• Combine clues logically. If clue 1 gives part of the order and clue 3 gives another part, see where they overlap or connect.
• Use process of elimination. Once a person's position or relationship is fixed, eliminate possibilities for other people.
• Check your final arrangement against all the original clues to ensure consistency.

These steps can help you systematically solve various types of ordering or ranking puzzles.