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Question
How do I solve this if I don't know the time/number of hours the flights took?
A jet flew from Tokyo to Bangkok, a distance of 4800km. On the return trip, the speed was reduced by 200km/hr. If the difference in flights was 2 hours, what was the jet's speed from Bangkok to Tokyo?
Hello Triceps
Let’s assume the initial speed was X, meaning the returning speed is X – 200 km/hr.
And T be the initial time, which implies the returning time is T + 2 hrs.
The distance is 4800km.
4800km = X*T
4800km = (X – 200) * (T + 2)
The distance never changes.
This means;
X*T = (X – 200) * (T + 2)
XT = XT + 2X – 200T – 400
400 + 200T = 2X
200 + 100T = X
Now use the first equation
4800 = (200 + 100T) * T
4800 = 200T + 100T2
48 = 2T + T2
T2 + 2T – 48 = 0
Use the quadratic formula to find the value of T
T = 6hrs.
Now you can substitute T = 6 in one of the equations and find X, the initial speed.
4800 = 6*X
800km/hr = X
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