The World's Shortest IQ Test, and Most of Us Fail

I was so proud of myself, absolutely certain I'd outsmarted a simple IQ test. It's a three question test, and it's frankly not complicated if you stop and think the problems through before answering quickly. But when I checked my answers against the correct answers, I had missed the first question. Got it completely wrong.

It's called the Cognitive Reflection Test and has been around since 2005, so it's not new. But lately, it's been making the rounds online.

Ready to test yourself? Here are the three questions:

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

2. It takes five machines five minutes to make five widgets. How long would it take 100 machines to make 100 widgets?

3. There's a patch of lily pads in a lake. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long will it take to cover half of the lake?

Make note of your answers, before checking for the correct answers below.


These are the most common answers given, but just because it's the popular answer doesn't make it the correct answer. In fact, all of these answers are wrong:

  1. 10 cents
  2. 100 minutes
  3. 24 days

Keep going, and I'll give you the actual right answers.

The correct answers are as follows:

  1. Five cents -- Most people went with 10 cents, but remember, the bat cost a dollar more than the ball. If the ball cost a dime, the bat would have to cost $1.10, making the total $1.20. So that doesn't work. But if the ball costs just a nickel, the bat costs $1.05. $1.05 + $0.05 = $1.10.
  2. Five minutes -- People get messed up by thinking it takes a minute to make a widget, but it's actually five minutes to make a widget. But because you had five machines, you were able to make all five of them in five minutes. If you're making 100 widgets and have increased the number of machines to 100, then you still can make all your widgets.... in five minutes.
  3. 47 Days -- Don't get messed up by thinking the lily pads increase the same amount each day, which is why most people came up with the wrong answer of 24 days. This is exponential growth at a consistent rate, i.e., 1+1=2, then 2+2=4, then 4+4=16. To fill up the lake on the 48th day, it would need to be half full of lily pads on the 47th day.

Feel really proud if you got all three, because only 17% of us can say that. I'm not among that elite group. sigh...

If you want to read more about the science behind why we get the bat and ball question wrong, read HERE.

[Photos: Getty Images]



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