SOLUTION: A Jet flew from Montreal to San-Francisco, a distance of 4000 km. On the return trip the speed was increased by 300km/h. If the total trip took 13h, what was the speed from Montre

Algebra ->  Pythagorean-theorem -> SOLUTION: A Jet flew from Montreal to San-Francisco, a distance of 4000 km. On the return trip the speed was increased by 300km/h. If the total trip took 13h, what was the speed from Montre      Log On


   

Question 257355: A Jet flew from Montreal to San-Francisco, a distance of 4000 km. On the return
trip the speed was increased by 300km/h. If the total trip took 13h, what was the speed from Montreal to San-Francisco?
Answer by drk(1908) About Me  (Show Source):
You can put this solution on YOUR website!
This is an RTD problem. We can create a table based on the given information
JET . . . . . . rate . . . . . . . . . .time . . . . . . . . . . . . . . . . distance
m->s . . . . R . . . . . . . . . . . .4000/R . . . . . . . . . . .. . . .. 4000
s->m . . . . R + 300 . . . . . . .4000/(R + 300) . . . . . . .. . .4000
totals . . . . . . . . . . . .. . . . . .. . .13
So, from the table, we get
4000%2FR+%2B+4000%2F%28R%2B300%29+=+13
multiply by common denominator to get
4000%28R+%2B+300%29+%2B+4000R+=+13%28R%29%28R%2B300%29
simplifying, we get
8000R+%2B+1200000+=+13R%5E2+%2B+3900R
setting = 0, we get
13R%5E2+-+4100R+-+1200000+=+0
By quadratic, we get
R = 500