Betty can mow a lawn...

Question

Betty can mow a lawn in 40 minutes. Melissa can mow the same lawn in 60 minutes. How long does it take for both Betty and Melissa to mow the lawn if they are working together? Express your answer as a reduced fraction.

Answer 1

Time = 1 / Combined Rate

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

= 1 / (1/24)

= 24 minutes

Answer 2

rate of work by Betty on this job is 1/40 of job per minute; Melissa's rate is 1/60 (slower because lower rate).

 

Entire job completed by working together: 1 = t(1/40+1/60)

 

Just solve for t (minutes).