Ann cleans an apartment in 12 hours and liz cleans an apportment in 18 hours. How long would it take to clean an appartment together?

Question

asked Oct 25, 2018 80.7k views

1 Answer

Jim Munro · Answer 1 · 2018-10-30T02:03:30+0000

If Ann cleans in 12 hours then she cleans
(1)/(12)

of the apartment per hour. Similarly Liz cleans
(1)/(18)

of the appartment per hour. So together then can clean
(1)/(12)+(1)/(18)=(5)/(36)

of the apartment for hour. Therefor it will take them
(36)/(5)=7.2

hours to clean.

The general formula
R_(c)=(AB)/(A+B)

can be used as a check if needed.