A technician makes a round-trip to and from a certain service center by the same route. If the technician completes the drive to the center and then completes 80 percent of the drive from the center, what percent of the round-trip has the technician completed? Pick one:  A) 50  B) 60  C) 70  D) 80  E) 90

Rationale: "round trip means 2 trips i . e . to and fro . he has completed one i . e 50 % completed . then he traveled another 80 % of 50 % i . e 40 % . so he completed 50 + 40 = 90 % of total trip . e"
Answer: E