In a flight of 600 km , an aircraft was slowed down due to bad weather. Its average speed for the trip was reduced by \(200~km/hr\) and the time of flight consequently increased by 30 minutes. The duration of the flight was:
A. 1 hour
B. 1.5 hours
C. 2 hours
D. 2.5 hours
Explanation: Let, speed be S and time be T. Now, \(ST=600\). Again, \((S-200)*(T+0.5)=600\). Or, \(ST - 200T + 0.5S - 100 = 600\). Or, \(200T - 0.5S + 100 = 0\). Or, \(200 T^2 + 100 T - 300 = 0\); \([S=600/T]\). Or, \(2T^2 + T - 3 = 0\). Or, \((2T+3)(T-1)=0\). Or, \(T = -3/2, 1\). So, flight টির duration ছিলো \(1 + 0.5\) hours = \(1.5\) hours.
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