Problem on rates

Question

Dr. Kanbir paints a room in 8 hours by himself while Isaac paints the same room in 6 hours. They

want to paint the room together. One hour after Dr. Kanbir starts painting, Isaac joins him. How

many hours did they paint together?

Answer 1

1/8 + 1/6 = 1/T

3T + 4T = 24

7T = 24

T= 24/7 = 3 3/7 hours working together

in 1 hour alone, Dr. K does 1/8 of the room, leaving 7/8 to go to paint together

this should take a little more time than 3 3/7 hours to finish

and a little less than 3 3/7 hours working together

they did a full room together in 3 3/7 hours

they can do 7/8 of a room in 7/8 x 24/7 = 24/8 = = 3 hours

they will work 3 hours together if Dr K works for one hour alone

Dr K will work for 4 hours and Isaac for just 3 hours to finish painting