#### Answer

It will take 1.75 hours, which is equal to 1 hour and 45 minutes, for the planes to be 1925 km apart.

#### Work Step by Step

Let t represent the time it will take the planes to be 1925 km apart.
The first plane travels to the left at 500 km per hour.
The second plane travels to the right at 600 km per hour.
The distance the first plane travels until both planes are 1925 km apart is 500 $\times$ t.
The distance the second plane travels until both planes are 1925 km apart is 600 $\times$ t.
Since the distance is 1925, we set up the following equation:
500t + 600t = 1925
1100t = 1925
Divide both sides by 1100
t = 1.75
It will take 1.75 hours for the planes to be 1925 km apart.