Walking at 4/7 of its usual speed, a train is 9 minutes late. Find its usual time to cover the journey.	Choose the correct choice from the following answers:
A) 8min. B) 10min. C) 12min. D) 15min. E) 17min.
Explanation :   Solution: New speed = 4/7 of the usual speed. Let usual time be x.   .'. New time taken = 7/4 of usual time = 7x/4   so, (7x/4 ) - x = 9 min.   =&gt; 3x = 36   =&gt; x = 12 min.   Answer : 12min.
<result>C</result>
Walking at 4/7 of its usual speed, a train is 9 minutes late. Find its usual time to cover the journey.