Answer:
Average speed of car in the first trip is 10 km/hr
Explanation:
It is given that first the car drives 6 hours to the east
Then travels 12 km to west in 3 hours
Average speed for the entire trip = 8 km/hr
Total time = 3+6 = 9 hour
So distance traveled in 9 hour = 9×8 = 72 km
As the car travel 12 km in west so distance traveled in east = 72-12 = 60 km
Time by which car traveled in east = 6 hour
So speed
So average speed of car in the first trip is 10 km/hr
The ducks' flight path as observed by someone standing on the ground is the sum of the wind velocity and the ducks' velocity relative to the wind:
ducks (relative to wind) + wind (relative to Earth) = ducks (relative to Earth)
or equivalently,
(see the attached graphic)
We have
Then by setting components equal, we have
We only care about the direction for this question, which we get from the first equation:
or approximately 136º or 224º.
Only one of these directions must be correct. Choosing between them is a matter of picking the one that satisfies <em>both</em> equations. We want
which means <em>θ</em> must be between 180º and 360º (since angles in this range have negative sine).
So the ducks must fly (relative to the air) in a direction 224º relative to the positive horizontal direction, or about 44º South of West.
