Question

It would take Mary 3 hours to paint her bedroom by herself. Her older brother Brian could paint the room in 8 hours. Working together, how long would it take for Mary and Brian to paint the room?

Answer 1

Working together, Mary and Brian will be able to paint the room in ²⁴⁄₅ hours. The calculation involves summing their individual rates of work and finding the reciprocal of the combined rate.

Step-by-step explanation:

Calculating Combined Work Time

Mary can paint her room in 3 hours, so her work rate is ⅓ of the room per hour. Brian can paint the room in 8 hours, which means his work rate is ⅛ of the room per hour. To find out how long it will take for both of them to paint the room together, we add their rates of working:

Mary's rate: ⅓ (room/hour)
Brian's rate: ⅛ (room/hour)
Combined rate: ⅓ + ⅛ = ⅜ (room/hour)

To find the number of hours it takes for them to paint the room together, we calculate the reciprocal of their combined rate:

1 / ⅜ (room/hour) = ²⁴⁄₅ hours

Thus, working together, it will take Mary and Brian ²⁴⁄₅ hours to paint the room.

Answer 2

3hrs to paint by Mary

8hr for Brian to paint

so together, Brian and Mary mean you add the two

together 3hrs

and 8hrs

equals 11 hrs

3+8=11