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 together
1 job 1 job
---------- + -------------
4 days 10 days
This comes out to:
1 job
------------------------------------------- = time required
10 job-days 4 job-days
------------------ + -----------------
40 days 40 days
or:
1 job
-------------------- = (40/14) days, or 20/7 days (just less than 3 days)
14 job·days
-----------------
40 days
