Sue​, an experienced shipping​ clerk, can fill a certain order in 6 hours. Felipe​, a new​ clerk, needs 11 hours to do the same job. Working​ together, how long will it take them to fill the​ order?

Answer 1

1/6 + 1/11 = 1/T

multiply by 66T to eliminate the fractions

11T + 6T = 66

17T = 66

T = 66/17 = slightly more than 3.88 hours working together

the average of 6 and 11 = (6+11)/2 = 17/2 = 8.5 hours divide by 2 = 8.5/2 =4.25 hours

Had they both done the work in 8.5 hours, together they'd do it in 4.25 hours

the larger the disparity between their individual times, the less than average time would be the hours for doing it together. 4.25 - 3.88 = 0.37 or a about 1/3 of an hour. Take the average and expect the answer to be slightly less