Answer :
Amount of time needed by Alanna to detail a car = 45 minutes
Amount of time needed by Robbie to detail a car = 30 minutes
Then
The time needed by
Alanna and Robbie to detail a car together = (30 * 45)/(30 + 45) minutes
= 1350/75 minutes
= 18 minutes
From the above deduction, we can conclude that the correct option among all the options that are given in the question is the second option or option "B". I hope it helped you.
Amount of time needed by Robbie to detail a car = 30 minutes
Then
The time needed by
Alanna and Robbie to detail a car together = (30 * 45)/(30 + 45) minutes
= 1350/75 minutes
= 18 minutes
From the above deduction, we can conclude that the correct option among all the options that are given in the question is the second option or option "B". I hope it helped you.