Final answer:
To find out how close the car will be to its destination after 3 hours, we calculate the distance traveled (120 km/h × 3 h = 360 km) and subtract it from the starting distance (400 km - 360 km = 40 km). Hence, the car will be 40 km from its destination.
Step-by-step explanation:
To determine how close the car will be to its destination after traveling at a constant speed of 120 km/h for 3 hours, we need to calculate the distance it covers in that time. The distance traveled is the product of the speed and the time of travel. Using the formula:
Distance = Speed × Time
The distance traveled by the car is:
Distance = 120 km/h × 3 h = 360 km
Since the car starts 400 km away from its destination, we subtract the distance traveled from the initial distance to find the remaining distance:
Remaining Distance = Initial Distance - Distance Traveled
Remaining Distance = 400 km - 360 km = 40 km
Therefore, the car will be 40 km away from its destination after 3 hours of travel at 120 km/h, which corresponds to option (a).