Question 25
A person takes 20 minutes more to cover a certain distance by decreasing his speed by 20%. What is the time taken to cover the distance at his original speed ?
Solution
Let the distance and original speed be 'd' km and 'k' kmph, respectively.
d/0.8k - d/k = 20/60 => 5d/4k - d/k = 1/3
=> (5d - 4d)/4k = 1/3 => d = 4/3 k
Time taken to cover the distance at the original speed
= d/k = 4/3 hours = 1 hour 20 minutes.
Option B is correct answer.
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