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In a race of one kilometre, A gives B a start of 100 metres and still wins by 20 seconds. But if A gives B a start of 25 seconds, B wins by 50 metres. The time taken by A to run one kilometre is
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- 17 seconds
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500 seconds 29 -
1200 seconds 29 -
700 seconds 29
Correct Option: B
Let A take x seconds in covering 1000m and b takes y seconds
According to the question,
| x + 20 = | y | |
| 1000 |
| ⇒ x + 20 = | ...(i) | |
| 10 |
| and, | x + 25 = y ...(ii) | |
| 1000 |
From equation (i),
| + | = y | ||
| 9 | 9 |
| ⇒ | + | = | + 25 | |||
| 9 | 9 | 1000 |
| ⇒ | + | = | + 25 | |||
| 9 | 9 | 20 |
| ⇒ | − | = 25 − | |||
| 9 | 20 | 9 |
| = | = | ||
| 180 | 9 |
| ⇒ | = | ||
| 180 | 9 |
| ⇒ x = | × | = | seconds. | |||
| 9 | 29 | 29 |
