Wendy cleaned 1/6 of a room in 2h. Lenna cleaned 1/3 of the same room in 1/2h. If they worked together, how long do they need to clean the room?
For this question, we need to find the 'speed' that they cleaned the room in the same unit of time. Let's use 1 hour here.
Wendy -> 2h -> 1/6 room
-------> 1h -> 1/6 divided by 2 = 1/6 x 1/2 = 1/12 room
Lenna -> 1/2h -> 1/3 room
-------> 1 h -> 1/3 x 2 = 2/3 room
Together -> 1h -> 1/12 + 2/3 = 3/4 room
Room is taken as 1 whole.
Time taken to clean room = 1 divided by 3/4 = 4/3h = 1&1/3h
