Try the world's shortest IQ test to know if you are smarter than 80% of the population

Editor's note: This article was originally published on October 30, 2023. It has since been updated.

The Cognitive Reflection Test (CRT), often hailed as the world's shortest IQ test, has gained renewed attention on the internet. This brief IQ test, consisting of only three questions, claims that if you complete it, you possess higher intelligence than 80% of the population. It was created in 2005 by former MIT Professor Shane Frederick, who teaches at Princeton. This quick IQ test aims to identify individuals with exceptional intellectual abilities, claiming to determine if their intelligence surpasses that of 80% of people worldwide. In a TikTok video, @_notjustjosh proceeded to present the three seemingly straightforward yet tricky questions, which have puzzled many since their inception.

The CRT IQ test consists of just three questions. The first question goes like this: "A bat and a ball cost a dollar and $1.10 in total. The bat costs $1 more than the ball. How much does the ball cost?" Although it may seem straightforward, it has been known to confuse people and has circulated on the internet. Moving on to the second question: "If it takes five machines five minutes to make five widgets, how long does it take 100 machines to make 100 widgets?" This question challenges your ability to reason about the relationship between the number of machines and the time taken to produce widgets.

The third question also involves numbers: "In a lake, there's a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long does it take for the patch to cover half of the lake?" This question tests your understanding of exponential growth. These three deceptively simple questions have been used to assess cognitive reflection. They have intrigued many people due to their tricky nature.

TikTok user Nathan Kennedy, who goes by @newmoneynate, renowned for his financial advice, finally unveiled the long-awaited answers to the CRT test in a video and provided in-depth explanations for each question. He guided viewers through the three questions and highlighted the common pitfalls many encounter with these deceptively simple-looking problems. Kennedy's insights shed light on the tricks and misconceptions hidden within the questions, helping viewers understand the correct thought processes required to solve them accurately.

According to Kennedy's explanations, the correct answer to the first question is $0.05, not $0.10 as many initially guess. The trap lies in assuming the ball costs $0.10 less than the bat, which would lead to an incorrect calculation. For the second question, Kennedy confirms that 100 machines would produce 100 widgets in 5 minutes. Each machine maintains the same efficiency of producing one widget in 5 minutes, so having 100 machines simultaneously working on 100 widgets results in the same time frame. Regarding the third question, Kennedy clarifies that it would take 47 days, not the intuitive 24 days, for the patch of lily pads to cover half the lake. The confusion stems from the pattern of doubling each day, making it appear that half the lake would be covered in half the time it takes to cover the entire lake.

Kennedy's insights into these questions demonstrate the effectiveness of the CRT test in challenging test takers to question their initial assumptions and think critically to arrive at the correct answers. That being said, the CRT test is not a definitive gauge of an individual's cognitive ability.