painter 1 can paint a room in 12 hrs
so in 1 hrs he can paint 1/12 part of a room
painter 2 can paint a room in 10 hrs
so in 1 hrs he can paint 1/10 part of a room
together in1 hrs they can paint (1/12 + 1/10) part of a
room = ( 5 + 6)/60 = 11/60 > LCM = 60
thus no. of hrs to complete the room = 60/11 ~ 5.45hrs