A and B start walking towards each other at 6pm at speed of 4kmph and 6kmph. They were initially 18km apart. At what time do they meet? Choose one.
A) 8 pm
B) 6 pm
C) 7 pm
D) 10 pm
E) 5 pm

Rationale: "time of meeting = distance / relative speed = 18 / 6 + 3 = 18 / 9 = 2 hrs after 6 pm = 8 pm answer is a"
Answer: A