Correct Answer - Option 3 : 3 hour
Given∶
Speed of Alpha = 60 kmph
Speed of Beta = 80 kmph
Formula Used∶
Time = Distance / Speed
Calculation∶
Distance covered by Alpha in 1 hour = 60 km
Beta starts after 1 hour, he is driving with the speed of 80 kmph
Relative speed of Alpha and Beta = 80 kmph – 60 kmph = 20 kmph
Hence, they will meet in = Distance covered by Alpha / Relative speed = 60 / 20 = 3 hr.
∴ Alpha and Beta will meet after 3 hours.