A developer is using a large language model to solve simple physics word problems. They provide the following example in their prompt to guide the model:

Question: A car accelerates from rest to 20 m/s in 5 seconds. What is its acceleration? Answer: 4 m/s²

When the developer then asks the model to solve a new problem, the model provides an incorrect answer. Based on principles of effective prompt design for reasoning tasks, analyze the developer's example and explain why it is likely failing to guide the model effectively. Then, describe how you would rewrite the example to improve the model's performance.