Final answer:
To find out how long it will take for Ken to paint the entire room, It will take Ken 1 hour and 12 minutes to paint the entire room.
Step-by-step explanation:
To find out how long it will take for Ken to paint the entire room, we can use the information given. Ken painted 3/4 of the room in 9/10 of an hour. Let's first find out how long it takes Ken to paint 1/4 of the room by dividing 9/10 by 3. It will take him 3/10 of an hour to paint 1/4 of the room.
Now, we can figure out how long it will take Ken to paint the entire room. Since 1/4 of the room takes him 3/10 of an hour, then 1 whole room would take him 4 times longer. Therefore, it will take Ken 12/10 of an hour or 1 hour and 12 minutes to paint the entire room.