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?

Answer 1

rate1=vat/2hrs
rate2=vat/4hrs

so in 4 hours, three vats could be emptied.

combined rate= 3 vats/4hrs

time= 1vat/combinedrate= 1.333 hrs