Kate wants to buy a special pen as a gift for her friend. The pen costs $30, and Kate only has money for a third of that amount. How much more money does she need to buy the pen? Give me reasons, before answering the question
Currently, Kate has only 1 / 3 * 30 = $10. That means Kate needs 30 - 10 = $20 more to buy the pen. So the final answer is 20.