Tuesday, August 10, 2010

A Riddle for My Readers

Question: A bat and a ball, together, cost a total of $1.10. The bat costs $1 more than the ball. How much is the ball?

The answer is not 10 cents.


Transplanted Lawyer said...

This is high school algebra stuff.

Total price is $1.10. The ball costs an unknown amount, x, and the bat costs $1.00 more than the ball. Therefore:
1.10 = x + (1 + x)

Which is simplified as:
1.10 = 2x + 1

Subtract the common integer (1) from both sides of the equation and you get:
.1 = 2x

Which means:
.05 = x

So the ball costs five cents.

What's the relevance?

Anonymous said...

The ball is free. The price of $1.10 reflects the following:

Bat: $1.00
Ball: $0.00
California Sales Tax: 10 cents

(This is based on San Francisco's sales tax of 9.5 percent. In some counties in California, the sales is lower.)

Am I correct? If yes, what is the prize?

Anonymous said...


Here's the answer:

The bat: $1.05
The ball: .05

This means that the bat is exactly one dollar more than the ball. Hence, the total is $1.10.

-Genius Brain at Work

P.S. This answer deserves a major prize. However, if you're intimidated by my brain, I understand.

Anonymous said...

I like the "ball is free" answer. :-) I'm guessing this has something to do with general innumeracy. The instinct is to say the bat is $1 and the ball is 10 cents, without immediately realizing that the difference is 90 cents.

K_Yew said...

@Transplanted: There is no relevance to the law. I just copied a riddle I picked up from the wonderful book, _The Ascent of Money_ by Niall Ferguson. He uses the riddle to make a point about cognitive traps, and how most human beings are "hardwired" for fallibility. Thank you for the detailed explanation.