1. **State the problem:** A car accelerates uniformly at 25 m/h per second. After 15 minutes, its speed is 120 km/h. We need to find the initial speed in km/h. 2. **Understand the units and formula:** The acceleration is given as 25 m/h per second, which means the speed increases by 25 meters per hour every second. 3. **Convert acceleration to consistent units:** Since the final speed is in km/h and time is in minutes, convert acceleration to km/h per second: $$25 \text{ m/h per second} = \frac{25}{1000} \text{ km/h per second} = 0.025 \text{ km/h per second}$$ 4. **Convert time to seconds:** 15 minutes = $15 \times 60 = 900$ seconds. 5. **Use the formula for uniform acceleration:** $$v = u + at$$ where - $v$ is the final speed, - $u$ is the initial speed, - $a$ is the acceleration, - $t$ is the time. 6. **Plug in the known values:** $$120 = u + 0.025 \times 900$$ 7. **Calculate the increase in speed:** $$0.025 \times 900 = 22.5$$ 8. **Solve for initial speed $u$:** $$u = 120 - 22.5 = 97.5$$ 9. **Final answer:** The initial speed of the car is **97.5 km/h**.