1. A bat and a ball cost $1.10 in total. The bat costs $1 more than the ball. How much does the ball cost?
- 5 cents – There's a very good chance you guessed 10 cents. The answer is actually a little less – a 5 cent ball plus a bat costing $1.05 will set you back $1.10. And, of course, $1.05 is exactly $1 more expensive than 5 cents. (A Princeton study found that people who responded 10 cents were "significantly" less patient than those who got the right answer.)
2. If it takes 5 machines 5 minutes to make 5 widgets, how long would it take 100 machines to make 100 widgets?
- 5 minutes – Your gut instinct might be to say 100 minutes. Fortunately, it wouldn't take quite so long. From the question, we can determine it takes exactly 5 minutes for 1 widget machine to make 1 widget. Therefore, it would take 5 minutes to make 100 widgets from 100 widget machines.
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?
- 47 days – You might have guessed 24 days. It seems intuitive to half the number of days because you're halving the size of the lilypad patch. But if the area of the lake covered in lilypads doubles every day, it would only take one day for it to go from being half covered to fully covered. Take one day away from 48 days and you're left with 47.