Find the speed of a train if an increase of 6kph lowers the time for a journey of 72 km by 10 minutes.
2 answers
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72/s = 72/(s+6) + 1/6
s^2 + 6s - 2592 = 0
(s+54)(s-48) = 0
speed = 48km/hr
time at 48km/hr: 1.5 hr = 90 min
time at 54km/hr: 4/3 hr = 80 min
s^2 + 6s - 2592 = 0
(s+54)(s-48) = 0
speed = 48km/hr
time at 48km/hr: 1.5 hr = 90 min
time at 54km/hr: 4/3 hr = 80 min