CBSE Class 10 Answered
Quadratic Equations.
Asked by khushal305 | 16 Nov, 2009, 07:01: PM
Expert Answer
Let the speed of the passenger train be x km/hr.
Total distance covered = 300 kms
Speed of the express train = (x + 30)km/hr
Time taken by the passenger train = (t + 2)hr
Time taken by the express train = t hr.
Now using the formula for speed.
x = 300/ (t+2) .......(2)
x + 30 = 300/t
t = 300/(x+30) ........(1)
Equating (1) in (2), we get
x = 300/ (300/(x+30) +2)
= 300/( (300+2x+60/ (x+30))
= 300 (x + 30)/ (360 + 2x)
360 x + 2x2 = 300x + 9000
2x2 + 60x - 9000 = 0
x2 + 30x - 4500 = 0
Solving this quadratic equation, we get x = 53.73 km/hr.
So, the speed of passenger train is 53.73 and the express train is 83.73.
Answered by | 17 Nov, 2009, 10:56: AM
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