Find out how smart you are in the world's shortest IQ test 5 years ago

Find out how smart you are in the world's shortest IQ test

How clever are you?

The Cognitive Reflection Test is called the shortest IQ test in the world and consists of just three questions.


It assesses individuals' ability to suppress an intuitive and spontaneous wrong answer in favor of a reflective and deliberative right answer. The quicker you get the correct answer, the smarter you are.

In a survey of almost 3,500 people, 33% got all three of the below questions wrong while 83% of those surveyed got at least one of the questions wrong.

According to Indy100, just 48% of MIT students surveyed were able to get all three questions correct.

Here are the three questions...

  1. A bat and a ball cost €1.10 in total. The bat costs €1.00 more than the ball.
    How much does the ball cost?
  2. If it takes 5 machines 5 minutes to make 5 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?

Take a couple of minutes and think about the answers. When you think you have them, scroll past the GIF of the Pug to see the correct answers...




Question One: The ball would actually cost 0.05c.

If the ball costs X, and the bat costs €1 more, then it will be:




Ball + Bat =X + (X+1) =1.1

Which means that

2X+1=1.1, and 2X=0.1

X= 0.05

Question Two: If it takes five machines five minutes to make five widgets, then it will take one machine five minutes to make one widget.


Therefore if 100 machines were all making widgets, it would take five minutes.

Question Three: The answer is 47 days.

If it doubles in size each day, then it would have to do the same going backwards. Hence, if it fills the entire lake after 48 days, it would cover half the lake the day before. Meaning the answer is 47 days.