Final answer:
The two buses will be 240 km apart at 11:00 a.m. after starting at 9:00 a.m.
Step-by-step explanation:
To find out at what time the two buses will be 240 km apart, we need to use the distance formula. Since the buses are traveling in opposite directions, their distances will be added together. Let's assume that they will meet in 't' hours. The distance covered by the first bus in 't' hours is 72t km, and the distance covered by the second bus in 't' hours is 48t km. So the equation becomes: 72t + 48t = 240. Combine like terms: 120t = 240. Divide both sides by 120 to solve for 't': t = 2. Therefore, the two buses will be 240 km apart after 2 hours. As they started at 9:00 a.m., they will be 240 km apart at 9:00 a.m. + 2 hours = 11:00 a.m. Therefore, the correct answer is C. 11:00 a.m.