A person takes 10 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? Choices:
A) 50 minutes
B) 20 minutes
C) 40 minutes
D) 60 minutes
E) 80 minutes
Let the distance and original speed be d km and k kmph respectively.   d/0.8k - d/k = 10/60 =&gt; 5d/4k - d/k = 1/6   =&gt; (5d - 4d)/4k = 1/6 =&gt; d = 4/6 k=2/3k   Time taken to cover the distance at original speed   = d/k = 2/3 hours = 40 minutes.   ANSWER:40 minutes
<result>C</result>
A person takes 10 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?