Flight 725 left New York at 10:28 a. m. flying north. Flight 245 left from the same airport at 11:18 a. m. flying south at one hundred twenty kph less than three times the speed of flight 725. At 1:06 p. m. they are 1,030 kilometers apart. What is the average rate of speed for Flight 245?

A) 165 kph

B) 395 kph

C) 365 kph

D) 345 kph

E) 155 kph

F) 175 kph

Step-by-step explanation:

Let x represent the average speed of flight 725.

Flight 725 left New York at 10:28 a. m. flying north.

Flight 245 left from the same airport at 11:18 a. m. flying south at one hundred twenty kph less than three times the speed of flight 725. This means that the speed of flight 245 is

3x - 120

At 1:06 p. m. they are 1,030 kilometers apart. This means that total distance travelled by both planes would be 1030

Between 10:28am and 1:06pm, the number of hours would be 2hr 38 minutes = 2 + 38/60 = 2.63 hours

Distance = speed * time

Total distance travelled by flight 725 = x * 2.63 = 2.63x

Between 11:18am and 1:06pm, the number of hours would be 1hr 48 minutes = 1 + 48/60 = 1.8 hours

Distance = speed * time

Total distance travelled by flight 245 = x * 1.8 = 1.8 (3x - 120)

5.4x - 216 + 2.63x = 1030

8.03x = 1030 + 216 = 1246

x = 1246/8.03 = 155 kph