Question

shawna can pour a large concrete driveway in six hours . Dan can pour the same driveway in seven hours. Find how long it would take them if they worked together?

Answer 1

work in  rates per hour :-

1/6 + 1/7 = 1/x

 Multiply through by the LCD,  42x:-

7x +  6x =  42

x = 42 / 13 = 3.23 hours answer

or about 3 hours 14 minutes