InterviewSolution
Saved Bookmarks
InterviewSolution
| 1. |
A train travels some distance at a constant speed. If the speed of the train would have increased by 15 km/hr, then it would have required 2 hours less. But if the speed of the train would have decreased by 5 km then to cover the same distance it would have required 1 hour more. Find the distance covered by the train. (1) 120 km (2) 240 km (3) 360 km (4) 400 km |
|
Answer» Correct option is (3) 360 km Speed x km/hr distance = y km Speed = (x + 15) \(\frac{\text{y}}{\text{x+5}}=\frac{\text{y}}{\text{x}}\) - 2 ⇒ xy = (x + 15) (y - 2x) ⇒ xy = xy + 15y - 2x2 - 30x ⇒ 15y = 2x2 + 30x Speed = (x – 15) km/hr \(\)\(\frac{\text{y}}{\text{x-5}}=\frac{\text{y}}{\text{x}}\) + 1 xy = (x - 5) (y + 5) ⇒ xy = xy + x2 - 5y - 5x ⇒ 5y = x2 - 5x ⇒ 15y = 3x2 - 15x ∴ 3x2 - 15x = 2x2 + 30x ⇒ x2 - 45x = 0 x = 0, x = 45 ∴ y = \(\frac{(45)^2}{5}\) - 45 = 405 - 45 = 360 km |
|