Answer:
1 1/12 hours to paint one room together
Explanation:
in 4 hour no of room painted by Tom = 1
dividing both side by four to find part of room painted in 1 hour
in 4/4 hour no of room painted by Tom = 1/4
so,
in 1 hour no of room painted by Tom = 1/4
similarly
in 3 hour no of room painted by Sam and Victor = 1
dividing both side by 3 to find part of room painted in 1 hour
in 3/3 hour no of room painted by Sam and Victor each = 1/3
so,
in 1 hour no of room painted by Sam and Victor each= 1/3
Total part of room painted by all of them working together in 1 hour
= 1/4 room + 1/3 room + 1/3room =(3 + 4+ 4) /12= 11/12 of room
Hence,
in 1 hour they paint together = 11/12 of the room
to find time taken to paint 1 full room
we divided both side by 11/12
in 1/(11/12) hour they paint together = 11/12/(11/12) of the room
in 12/11 hours they paint together = 1 room
Thus,
they take 12/11 hours i.e. 1 1/12 hours to paint one room together.
1 hour = 60 minutes
1/12 hours = 60/12 minutes = 5 minutes
thus, we can also say
they take 1 hours and 5 minutes to paint one room together.