3. Susan drives her car at an average speed of s miles per hour for t hours and travels 215 miles. Which of the following equations represents this information?
Answer: A
st = 215
The equation st = 215 accurately represents the relationship between speed, time, and distance traveled by Susan. In this case, the product of her average speed (s) and the time (t) she drives equals the total distance of 215 miles.
A) st = 215
This option is correct because it directly follows the formula for distance, which states that distance equals speed multiplied by time. Here, st represents the distance traveled, confirming the relationship described in the question.
B) 215 + t = s
This option is incorrect as it suggests that adding time (t) to the distance (215) gives the speed (s), which misrepresents the relationship between these variables. The equation does not follow the basic principles of distance calculation.
C) s/t= 215
This option is also incorrect because it implies that speed divided by time equals the distance, which is not a valid formulation. The correct formula for speed is distance divided by time (s = 215/t), not the other way around.
D) s + t = 215
This option is incorrect as it suggests that the sum of speed and time equals the distance, which is not a valid representation of the relationship between these variables. The equation misrepresents the fundamental relationship required to calculate distance.
Conclusion
The equation st = 215 is the only correct representation of the relationship between speed, time, and distance in this scenario. All other options fail either by misapplying the formula or by suggesting incorrect relationships among the variables involved. Thus, st = 215 is definitively the correct answer.