Did you guess that the ball would cost $.10? Most people do. The question (if you missed the question see it here) looks deceptively simple.
But if the ball did cost $.10 then the bat would cost $1.10 and the total would be $1.20. Most of us learned basic algebra in grade school. But to do the following in your head is more time consuming:
Total Cost = $1.10
Ball = X
Bat = X+1.00
So we are solving for $1.10 = X+(X+$1.00)
subtract $1.00 from both sides:
$.10 = 2X
dived both side by 2
$.05 = X
ANSWER: The ball costs $.05
For some reasons when we have to take time to read the more difficult to read version of the question we are more willing to take the time to do the algebra.
In Malcolm Gladwell's new book David and Goliath he explores some very interesting and counter intuitive phenomenons related to a variety ways that the underdog wins and wins big.