One pump can empty a pool in 4 days, whereas a second pump can empty the pool in 10 days. How long will it take the two pumps, working together, to empty the pool? (Fractional answers are OK.)

Answer: 20/7 days (just less than 3 days)Step-by-step explanation:Recall that (1 job) = (rate)(time), so time = (1 job) / (rate).Set up and solve the following equation:   1 job------------------------------- = time required for 2 pumps working together1 job         1 job---------- + -------------4 days      10 daysThis comes out to:               1 job------------------------------------------- = time required 10 job-days      4 job-days------------------ + -----------------    40 days           40 daysor:     1 job-------------------- = (40/14) days, or 20/7 days (just less than 3 days)14 job·days -----------------    40 days