This is the shortest IQ test in the world, but it is still one of the toughest.

Called the Cognitive Thinking Test, it is made up of just three math questions.

The quiz is not new, but was originally part of a research paper published in 2005 by MIT Professor Shane Frederick. This document has recently resurfaced online, leaving many people eager to give it a try and test their intelligence.

As part of his research, Professor Frederick took the test to over 3,000 participants from a variety of educational backgrounds – and even those who attend top US universities such as Yale and Harvard struggled to find all the answers. .

Of all those who participated, only 17% managed to get three out of three points on the test, which means that 83% of people failed.

Professor Frederick said: “The three elements of CRT are ‘easy’ in the sense that their solution is easily understood when explained, but achieving the right answer often requires removing a wrong answer that comes ‘impulsively’. in mind. “

Here are the questions:

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 create five widgets, how long would it take 100 machines to create 100 widgets?

3. In a lake, there is a square of water lilies. 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?

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These are the three most common answers people guess – but they’re actually incorrect.

1.10 cents

2.100 minutes

3. 24 days

Professor Frederick adds, “Anyone who thinks about it for a moment would agree that the difference between $ 1 and 10 cents is only 90 cents, not $ 1 as the problem states.

“In this case, detecting this error is tantamount to fixing the problem, because almost everyone who does not answer” ten cents “does, in fact, give the correct answer.”

The correct answers are:

1.5 cents

25 minutes

3. 47 days

Still puzzled by all of this? Fortunately, Presh Talwalkar, author of The Hoy of Game Theory: An Introduction to Strategic Thinking, explained how to find the right answers on his blog, Mind Your Decisions.

1. Suppose the ball costs X. Then the bat costs $ 1 more, so it’s 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 that the ball costs 5 cents and the bat costs $ 1.05.

2. If it takes five machines five minutes to create five widgets, then it takes a machine five minutes to create a widget (each machine makes a widget in five minutes). If we have 100 machines working together, each one can create a widget in five minutes. So there will be 100 widgets in five minutes.

3. Each day the patch doubles in size. So, every BACKWARDS day means that the patch size decreases by half. So, on day 47, the lake is half full.