# RE7 | deepseek/deepseek-v4-pro | run 1

## Prompt

A bat and a ball cost $1.10 together. The bat costs $1.00 more than the ball. How much does the ball cost?

## Response

The ball costs **$0.05** (5 cents). Many people initially answer 10 cents, but if the ball were $0.10 and the bat cost $1.00 more, the bat would be $1.10, making the total $1.20. The correct solution requires solving \(x + (x + 1.00) = 1.10\), giving \(x = 0.05\).

This is a classic question from the Cognitive Reflection Test, which measures the tendency to override an intuitive but incorrect answer with a more analytical one [Cognitive Reflection Test](https://en.wikipedia.org/wiki/Cognitive_reflection_test).

Would you like to try another brain teaser?
