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In a flight of 600 kms, an aircraft was slowed down due to bad weather. Its average speed for the trip was reduced by 200 km per hr. and the time of flight increased by 30 minutes. Find the duration of flight.
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- 1.2 hours
- 1 hour
- 1.5 hours
- 2 hours
Correct Option: B
Let the original speed be x kmph
then, new speed = (x – 200) kmph
According to question,
Time taken with new speed – time taken with original speed
| = 30 min. i.e | hr. | |
| 2 |
| ∴ | − | = | |||
| x − 200 | x | 2 |
| ⇒ 600 |  | − |  | = | |||
| x − 200 | x | 2 |
| ⇒ | = | ||
| x(x − 200) | 1200 |
⇒ 24000 = x (x – 200)
⇒ x2 – 200x – 24000 = 0
⇒ x2 – 600x + 400x – 24000 = 0
⇒ x (x – 600) + 400 (x – 600) = 0
⇒ (x – 600) (x + 400) = 0
⇒ x = 600, – 400
Speed cannot be negative
Hence, original speed = 600 kmph and duration of flight
| = | hr. = 1 hr. | |
| 600 |
