Question

4. Robert can paint a wall in 10 minutes, and Jack can paint the same wall in 26 minutes. How long will it take them to paint a wall together? Round to two decimal places.

Answer 1

how much of a wall can jack do in a minute? j
how much of a wall can robert do in a minute? r

r+j = amount of wall they finish in a minute together

Answer 2

the thing is: r+j is a rate of wall per minute, and you want a rate of minute per wall so we have to flip for the solution.

Answer 3

1/10 + 1/26, is the rate of wall per minute