# The “world’s shortest” IQ test only has three questions and a 17 per cent pass rate

IQ tests are a handy and practical way of figuring out how smart you are.

Typically, the tests can be quite long, lasting over an hour with a variety of questions designed to test your brain to its limits. Despite this, many brainiacs may be surprised to learn that there is an IQ test out there with only three questions.

However, the shortness of the test doesn’t mean it’s any less difficult. In fact, a study revealed that only 17 per cent of participants were able to pass the brain teaser. Known as the Cognitive Reflection Test, the quiz was originally part of a research paper published in 2005 by MIT professor Shane Frederick, the Mirror reports.

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Since resurfacing online, the paper has gone viral as people rush to see if they can smash the “world’s shortest IQ test”. As part of the study, Professor Frederick made more than 3,000 participants from a range of educational backgrounds complete the IQ test.

From that large group of people, only 17 per cent managed to score three out of three on the test. Speaking about the test, Professor Frederick, said: “The three items on the CRT are ‘easy’ in the sense that their solution is easily understood when explained, yet reaching the correct answer often requires the suppression of an erroneous answer that springs ‘impulsively ‘ to mind.”

### What are the questions?

Read below to look at the three questions included in the short IQ test:

1. A bat and a ball cost \$1.10 in total. The bat costs \$1 more than the ball. How much does the ball cost?

2. If it takes five machines five minutes to make five widgets, how long would it take 100 machines to make 100 widgets?

3. In a lake, there is 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 would it take for the patch to cover half of the lake?

Below you will find the three most common answers which are in fact all wrong:

1. 10 cents

2. 100 minutes

3. 24 days

Professor Frederick adds: “Anyone who reflects upon it for even a moment would recognize that the difference between \$1 and 10 cents is only 90 cents, not \$1 as the problem stipulates.

“In this case, catching that error is tantamount to solving the problem, since nearly everyone who does not respond ’10 cents’ does, in fact, give the correct response.”

### What are the correct answers?

1. 5 cents

2. 5 minutes

3. 47 days

If you’re still a bit confused by the answers even after reading them, an explanation for their equations has been provided by Presh Talwalkar, the author of The Hoy of Game Theory: AN Introduction to Strategic Thinking. He has provided the following explanations for each solution:

1. Say the ball costs X. Then the bat costs \$1 more, so it is X + 1. So we have bat + ball = X + (X + 1) = 1.1 because together they cost \$1.10. This means 2X + 1 = 1.1, then 2X = 0.1, so X = 0.05. This means the ball costs 5 cents and the bat costs \$1.05

2. If it takes 5 machines 5 minutes to make 5 widgets, then it takes 1 machine 5 minutes to make 1 widget (each machine is making a widget in 5 minutes). If we have 100 machines working together, then each can make a widget in 5 minutes. So there will be 100 widgets in 5 minutes.

3. Every day FORWARD the patch doubles in size. So every day BACKWARDS means the patch halves in size. So on day 47 the lake is half full.

www.manchestereveningnews.co.uk

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#### George Holan

George Holan is chief editor at Plainsmen Post and has articles published in many notable publications in the last decade.