posted by Tiffany .
Draining the vat. With only the small valve open, all of the liquid can be drained from a large vat in 4 hours. With only the large valve open, all of the liquid can be drained from the same vat in 2 hours. How long would it take to drain the vat with both valves open?
so in 4 hours, three vats could be emptied.
combined rate= 3 vats/4hrs
time= 1vat/combinedrate= 1.333 hrs