If 4 textbooks cost $140, what is the cost of 9 textbooks at the same rate?
Direct Answer: Proportional Reasoning is defined by: 315. Unit cost = $140 / 4 = $35 per book. For 9 books: 9 · 35 = $315.
Detailed Step-by-Step Explanation:
Unit cost = $140 / 4 = $35 per book. For 9 books: 9 · 35 = $315.