Janet can shovel snow from her driveway in 40 minutes. Jim can do the same job in 50 minutes. How long would it take Janet and Jim to shovel the driveway if they worked​ together?

Answer 1

1/40 + 1/50 = 1/X

50X + 40X = 2000

90X = 2000

X = 200/9 = 22.22... minutes working together

If they both could do it in 45 minutes each, together they'd do it in half the time = 22.5 minutes

while 45 is the average of 40 and 50, the 40 will skew their combined time slightly less than 22.5

in 22 2/9 minutes Janet can do (22 2/9)/40 of the job = 200/9/40 = 5/9

in 22 2/9 minutes Jim can do (22 2/9)/50 of the job = 200/9/50 = 4/9

5/9 + 4/9 = 1 = the full job completed