<PRE><B>Question 803384</B>
Filling or emptying the pool we consider as 1 job

Pump A takes 30 hours to do 1 job
so it does 1/30 of the jb in 1 hour

Similarly pump B does 1/36 of the job in 1 hour

Actual jbo done

1/30 -/36         LCD = 180

(6-5)/180 

=1/180 of the job is done in 1 hour

so it will take 180 hours to complete the job that is filling the pool</PRE>