A bat and ball cost $1.10 in total. The bat costs $1 more than the ball. How much does the ball cost?
Almost everyone who reads this question will have an immediate impulse to answer '10 cents.' I surely did. As Dan Gardner says, "It just looks and feels right. And yet it's wrong. It's clearly wrong--if you give it some careful thought--and yet it is perfectly normal to stumble on this test. Almost everyone we ask reports an initial tendency to answer 'ten cents,' write psychologists Daniel Kahneman and Shane Frederick. Many people yield to this immediate impulse. People are often content to trust a plausible judgment that quickly comes to mind." 1
