By walking at of his usual speed, a man reaches his office 20 minutes later than his usual time. The usual time taken by him to reach his office is:

By walking at of his usual speed, a man reaches his office 20 minutes

1.	By walking at of his usual speed, a man reaches his office 20 minutes later than his usual time. The usual time taken by him to reach his office is:
A.	75 minutes
B.	60 minutes
C.	40 minutes
D.	30 minutes
Answer» C. 40 minutes