I am unsure of what formula to use for this problem can anyone help me?

Lisa can shovel snow from her driveway in 60 minutes, Jim can do the same job in 55 minutes. How long will it take Lisa and Jim to shovel the driveway if they worked together?

3 answers

RateforLisa=1drive/60min
rateforJim=1drive/40 min

Now you have one drive to do.
both work the same amountof time.

1drive=ratelisa*time + ratejim(time)
1drive=(drive/60min + drive/40min )time

time=1/(1/60 + 1/40)

multiply the right side by 2400/2400
time=2400/(40+60) and you have it
Thank You!!!
Lisa can showel snow in 55 minutes. Bill can do the same job in 30 minutes. How long would it take if they worked together?