Final answer:
To construct an equation that relates the speeds of the two legs of the trip, let's start by representing the speed on the first leg as y mph. On the first leg of the trip, the time taken is 640/y hours. On the return trip, the speed is increased by 40 mph, making it x+40 mph. The time taken on the return trip is 640/(x+40) hours. According to the given information, increasing the speed by 40 mph on the return trip saved 4 hours. So we can set up the equation: 640/y - 640/(x+40) = 4. Simplifying this equation will give us the relation between the speeds of the two legs of the trip.
Step-by-step explanation:
To construct an equation that relates the speeds of the two legs of the trip, let's start by representing the speed on the first leg as y mph.
On the first leg of the trip, the time taken is 640/y hours.
On the return trip, the speed is increased by 40 mph, making it x+40 mph. The time taken on the return trip is 640/(x+40) hours.
According to the given information, increasing the speed by 40 mph on the return trip saved 4 hours. So we can set up the equation:
640/y - 640/(x+40) = 4
Simplifying this equation will give us the relation between the speeds of the two legs of the trip.