Walking 6/7th of his usual speed, a man is 12 minutes too late. What is the usual time taken by him to cover that distance?

New speed =6/7 of usual speed Speed and time are inversely proportional. Hence new time =7/6 of usual time Hence, 7/6 of usual time - usual time =12 minutes ⇒1/6 of usual time =12 minutes Therefore, usual time =12×6=72 minutes=1 hour 12 minutes