Question 454654
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 725?
:
Let s = speed of flt 725
then it says:
"Flt 245 at one hundred twenty kph less than three times the speed of flight 725."
therefore:
(3s-120) = speed of flt 245
:
Find the flying time of each aircraft change 1:06 to 13:06
Flt 725: 13:06 to 10:28: 12:66 - 10:28 = 2 hr 38 min or {{{158/60}}} = 79/30 hrs
Flt 245: 13:06 to 11:18: 12:66 - 11:18 = 48 min or {{{4/5}}} hrs
:
Write a distance equation: dist = speed * time
:
Flt 725 dist + Flt 245 dist = 1030 km
{{{79/30}}}s + {{{4/5}}}(3s-120) = 1030 
Multiply by 30, results:
79s + 6*4(3s-120) = 30(1030)
79s + 24(3s-120) = 30900
79s + 72s - 2880 = 30900
151s = 30900 + 2880
151s = 33780
s = {{{33780/151}}}
s = 223.7 km/hr is flt 725