World's Shortest IQ Test Comprises Three Questions And 83% Fail It

World's Shortest IQ Test Comprises Three Questions And 83% Fail It
Things like figures and calculations make life difficult for most of us. Aren’t we already occupied so many problems – ranging from personal to social and economic? Why these tests? Why people are so judgmental and test others through tests? We are told everyone enjoys the right to privacy, but why isn’t it applied to IQ? Why is it a public property?

The saddest thing is we never hear about any protest on the issue in any part of the world. So until your IQ isn’t listed under the right to privacy or at least the intellectual property rights, we are doomed to be tested by tests. So let’s check the story of one of these.

The world’s shortest IQ test in the world comprises just three questions, but fewer than one in five people get it right.

According to Daily Mirror, called the Cognitive Reflection Test, the quiz isn't new, but was originally part of a research published in 2005 by Prof Shane Frederick of MIT. This paper has recently resurfaced online, leaving many keen to give it a go.

As part of his research, Prof Frederick had more than 3,000 participants from a range of backgrounds complete the test - and even those attending top American universities such as Yale and Harvard struggled to work out all the answers.

Of all those who took part only 17 per cent managed to score three out of three on the test, meaning 83 per cent of people failed.

But why so difficult! What 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 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?


These are the three most common answers that people guess - but they are actually incorrect.

  1. 10 cents

  2. 100 minutes

  3. 24 days


Prof Frederick adds: "Anyone who reflects upon it for even a moment would recognise 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."

The correct answers are:

  1. 5 cents

  2. 5 minutes

  3. 47 days


Still puzzled by all of this? Thankfully, Presh Talwalkar, the author of ‘The Hoy of Game Theory: An Introduction to Strategic Thinking’ explained how to work out the correct answers.

  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, the lake is half full on day 47.

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