A fiendishly clever logic puzzle is sweeping social media, with reports suggesting a staggering 90% of people give up before finding the correct answer. The brainteaser, which demands sharp deductive reasoning and a keen eye for detail, offers the perfect mental workout to shake off any post-Christmas lethargy.
The Power of a Puzzling Mind
Engaging with puzzles and brainteasers is more than just a fun diversion. Regularly challenging your cognitive abilities is crucial for maintaining mental fitness, much like physical exercise is for the body. Such mental workouts can enhance problem-solving skills, boost cognitive function, and may even help in safeguarding long-term brain health. After a period of festive relaxation, this riddle provides an ideal cerebral kick-start.
Cheryl's Notorious Birthday Conundrum
The puzzle was popularised on Instagram by Thomas Mulligan, who highlighted that despite seeming simple initially, nine out of ten people cannot crack it. Originating from Singapore's National Institute of Education, it has since earned a reputation as one of the world's most famous logic puzzles.
The scenario is this: two friends, Albert and Bernard, want to know the birthday of their new friend, Cheryl. She gives them a list of ten possible dates:
- May 15, May 16, May 19
- June 17, June 18
- July 14, July 16
- August 14, August 15, August 17
Cheryl then privately tells Albert the month of her birthday and Bernard the specific day. The puzzle is solved through their subsequent conversation.
The Crucial Conversation
Albert states: "I don't know when Cheryl's birthday is, but I know that Bernard doesn't know either."
Bernard then responds: "At first I didn't know Cheryl's birthday, but now I know."
Albert concludes: "Then I also know."
Using only this exchange, the challenge is to deduce Cheryl's correct birthday.
Solving the Step-by-Step Logic
The solution hinges on a process of elimination based on the unique information each man has. Albert's first statement is key: he knows the month and is certain Bernard cannot know the answer. For this to be true, the month Albert knows cannot contain a day that is unique to the list. If Bernard had been told the 18th or 19th, he would know the birthday instantly (as only June 18 and May 19 appear). Therefore, Albert's month cannot be May or June, as they contain these unique days.
This initial deduction leaves only July and August as possible months. Upon hearing Albert's statement, Bernard is able to figure out the answer. This means the day Bernard knows must now be unique between July and August. The possible dates are July 14, July 16, August 14, August 15, and August 17.
Since the 14th appears in both July and August, and the 15th and 17th also appear in August (with the 15th in May too), they are not unique. The only day that appears once across these two remaining months is July 16th. Therefore, Bernard can now identify the date.
Finally, Albert can also deduce the answer. Knowing it is July 16th, he confirms the solution. So, after working through the layered clues, Cheryl's birthday is revealed to be July 16th.
Did you manage to unravel the logic and arrive at the correct date? This puzzle brilliantly demonstrates how systematic thinking and careful attention to given information can solve even the most baffling of problems.
