Question 717902
This is just combining two rates by addition.  Use the rates as records per minute.

50/2 + 50/3 = (50*3+50*2)/6={{{250/6}}}=


Keeping the rate in THAT form will make it easy to find how many minutes for 1000 records.  SIMPLE PROPORTION!   

{{{250/6=(250*4)/(6*4)}}}



....., 24 minutes.