Logical Reasoning Questions for CLAT | QB Set 113 [Evidence-Based Detective Puzzle]

Topic: Evidence-Based Detective Puzzle – Strongest Conclusion and Necessary Condition

Scenario

At 8:30 p.m., a confidential examination paper disappeared from the records room of a coaching institute. Five employees—Aarav, Bhavna, Chirag, Diya and Eshan—were present in the building between 8:00 p.m. and 9:00 p.m. Investigators established the following facts:

1. The records room could be opened only with either Aarav’s or Diya’s access card.
2. Electronic records show that Diya’s card opened the records room at 8:22 p.m.
3. At 8:22 p.m., Diya was visible continuously on a live video call from the reception desk until 8:35 p.m. Her access card, however, had been left unattended on her desk from 8:10 p.m. to 8:25 p.m.
4. Aarav’s card was used to enter the staff lounge at 8:18 p.m. and to leave it at 8:29 p.m. The lounge has only one entrance, and CCTV shows Aarav remained inside throughout that period.
5. Bhavna and Chirag were both seen in the corridor containing Diya’s desk between 8:15 p.m. and 8:20 p.m. Eshan was in a meeting room on another floor until 8:27 p.m.
6. The records-room camera captured the person entering at 8:22 p.m. wearing a dark jacket and carrying no bag. The person’s face was not visible.
7. Bhavna wore a light-coloured sweater throughout the evening. Chirag wore a dark jacket. Eshan also wore a dark jacket.
8. At 8:26 p.m., the missing paper was scanned using the photocopier beside the records room. The copier requires an employee PIN. The PIN used belonged to Chirag.
9. Investigators confirmed that employee PINs are memorised credentials and are not printed on identity cards or access cards. There is no evidence that Chirag had disclosed his PIN to anyone.

Assume that all electronic records, CCTV observations and stated timings are accurate.

Questions

1. Which of the following is the strongest conclusion supported by the evidence?

(A) Diya stole the examination paper because her card opened the records room.
(B) Chirag was the person who entered the records room at 8:22 p.m.
(C) Bhavna took Diya’s card and gave it to Eshan.
(D) Aarav and Chirag acted together to remove the paper.

2. Which of the following must necessarily be true if Chirag was the person who entered the records room?

(A) Chirag knew Diya’s access-card password.
(B) Diya voluntarily gave her card to Chirag.
(C) Chirag obtained possession of Diya’s access card before 8:22 p.m.
(D) Chirag entered the building before 8:00 p.m.

3. Which piece of evidence most strongly distinguishes Chirag from Eshan as the likely person who entered the records room?

(A) Both men wore dark jackets.
(B) Eshan was in a meeting room until 8:27 p.m.
(C) Diya’s card was left unattended.
(D) Aarav remained inside the staff lounge.

4. Suppose investigators later discover that Bhavna knew Chirag’s copier PIN. Which conclusion would then become substantially weaker?

(A) Diya could not personally have entered the records room at 8:22 p.m.
(B) Aarav could not have used Diya’s card at 8:22 p.m.
(C) Chirag was probably responsible for scanning the missing paper.
(D) Eshan could not have entered the records room at 8:22 p.m.

5. Which of the following additional facts would most strengthen the conclusion that Chirag entered the records room?

(A) Chirag had complained earlier that the records room was too small.
(B) Bhavna left the building at 8:40 p.m.
(C) A fingerprint matching Chirag was found on the inside door handle of the records room, and investigators confirmed it had been cleaned earlier that evening.
(D) Diya normally kept her access card in her handbag.

6. Which of the following statements is best supported by the evidence, even without assuming that Chirag was the thief?

(A) Whoever entered the records room must have personally known Chirag’s copier PIN.
(B) Diya’s access card was used by someone other than Diya at 8:22 p.m.
(C) Only Chirag had an opportunity to obtain Diya’s access card.
(D) The person who entered the records room must also have scanned the missing paper.

Answer Key

Detailed Explanations

1. Correct Answer: (B) Chirag was the person who entered the records room at 8:22 p.m.

The evidence converges most strongly on Chirag.

• The room was opened with Diya’s card.
• Diya could not personally have used it because she was continuously visible at reception.
• Chirag had access to the corridor where Diya had left the card unattended.
• The entrant wore a dark jacket, which matches Chirag.
• Eshan also wore a dark jacket, but he was in a meeting room on another floor until 8:27 p.m., so he could not have entered at 8:22 p.m.
• At 8:26 p.m., the missing paper was scanned using Chirag’s personal PIN, and there is no evidence that he shared it.

Thus, Chirag is supported by several independent pieces of evidence.

Option (A) conflicts with Diya’s verified location. Options (C) and (D) introduce facts for which there is no evidence.

2. Correct Answer: (C) Chirag obtained possession of Diya’s access card before 8:22 p.m.

The records room could be opened only using Aarav’s or Diya’s access card. The electronic record specifically shows that Diya’s card opened the room at 8:22 p.m.

Therefore, if Chirag entered the room, he must somehow have obtained Diya’s card before that time.

It is not necessary that Diya voluntarily gave it to him. The scenario expressly states that the card was unattended. Nor is there any access-card password mentioned in the facts. Chirag’s time of entry into the building is also irrelevant.

Hence, possession of Diya’s card before 8:22 p.m. is a necessary condition for Chirag’s entry.

3. Correct Answer: (B) Eshan was in a meeting room until 8:27 p.m.

The dark jacket alone cannot distinguish Chirag from Eshan because both wore one.

The crucial distinction is opportunity. The records-room entry occurred at 8:22 p.m., while Eshan remained in a meeting room on another floor until 8:27 p.m.

This effectively eliminates Eshan as the person captured entering the room.

Diya’s unattended card explains how someone might have gained access, but it does not distinguish between Chirag and Eshan by itself. Aarav’s location is relevant to Aarav, not to the comparison between Chirag and Eshan.

4. Correct Answer: (C) Chirag was probably responsible for scanning the missing paper.

Originally, the use of Chirag’s PIN at 8:26 p.m. strongly connects him to the scanning because PINs are memorised and there is no evidence of disclosure.

If investigators discover that Bhavna knew Chirag’s PIN, that inference becomes significantly weaker. Bhavna could potentially have entered the PIN herself.

The new fact would not alter the CCTV evidence showing Diya at reception. It would also not affect Aarav’s verified presence in the staff lounge or Eshan’s presence in the meeting room.

Therefore, only the inference concerning Chirag’s responsibility for the scanning is substantially weakened.

5. Correct Answer: (C) A fingerprint matching Chirag was found on the inside door handle of the records room, and investigators confirmed it had been cleaned earlier that evening.

This would provide strong physical evidence that Chirag had recently been inside the records room.

The fact that the handle had been cleaned earlier is important. Without it, Chirag’s fingerprint might have resulted from an earlier lawful visit. A recently cleaned surface makes a subsequently discovered fingerprint much more probative.

Option (A) has almost no connection to the offence. Bhavna’s departure time in (B) does not identify the entrant. Diya’s usual habit in (D) does not establish what happened on this particular evening.

Thus, (C) most strongly strengthens the conclusion.

6. Correct Answer: (B) Diya’s access card was used by someone other than Diya at 8:22 p.m.

Two established facts must be combined:

• Diya’s card opened the records room at 8:22 p.m.
• Diya was continuously visible at the reception desk at that time.

Therefore, someone other than Diya must have physically used her card.

Option (A) goes too far. The entrant and the person who later used Chirag’s PIN need not necessarily be the same individual.

Option (C) is false because both Bhavna and Chirag were near Diya’s desk and therefore had an apparent opportunity to obtain the card.

Option (D) is also unsupported because the evidence does not conclusively establish that the 8:22 p.m. entrant and the 8:26 p.m. copier user were the same person.

Thus, (B) is the strongest unavoidable inference from the evidence.