If a baseball and a bat cost $1.10 together, and the bat costs $1.00 more than the ball, how much does the ball cost?

This puzzle illustrates the difference between impulsive (or intuitive) and reflective (or analytical) thinking.

“The bat-and-ball problem is our first encounter with an observation that will be a recurrent theme: many people are overconfident, prone to place too much faith in their intuitions. They apparently find cognitive effort at least mildly unpleasant and avoid it as much as possible.”

Named the cognitive reflection test (CRT), it is also said to be a good indicator of how patient candidates are and how good they are at making decisions.

The test has been designed by Professor Shane Frederick of the MIT Sloan School of Management in America, who claims the questions are easy, in that their solution is easily understood when explained.

To arrive at the right answer candidates need to suppress the first response that springs ‘impulsively’ to the mind and instead work it out logically. But of the 3,000 students Professor Frederick tested, fewer than half gave the correct answer to the question about the relative cost of the bat and a ball.

The correct answer is 5 cents.  Don’t feel bad if you guessed 10 cents; you’re in good company.  If you even hesitated about your answer, that is a good sign!  Bottom line: Don’t jump to conclusions!

If you are entertained by this puzzle, here are two more:

1.  The number of water lillies on a lake doubles every day.  If it takes 48 days to cover the lake entirely, how long does it take to cover half the lake?

2. If it takes 5 machines 5 minutes to make 5 widgets, how long would it take 100 machines to make 100 widgets?

There are many more similar puzzles but these three are among the most popular.  It is good to be reminded that as simple as things may appear at first blush, and as obvious or complicated as a response may seem, we are often not as clever as we thought!  And just in case you want to verify, here are the answers to the last two questions:  47 days; 5 minutes