Final answer:
To calculate the speed of Puan Salini's car after 7 seconds, we add the initial speed to the product of acceleration and time, giving us a final speed of 132 km/h.
Step-by-step explanation:
To calculate Puan Salini's car speed after 7 seconds of acceleration at 6 km/h per second from an initial speed of 90 km/h, we use the following formula:
Final speed = Initial speed + (Acceleration × Time).
Given: Initial speed = 90 km/h, Acceleration = 6 km/h², Time = 7 s.
We plug in the values:
Final speed = 90 km/h + (6 km/h² × 7 s)
Final speed = 90 km/h + 42 km/h
Final speed = 132 km/h.
Therefore, after 7 seconds, the speed of Puan Salini's car would be 132 km/h.