It takes pipe A 10 days to fill a fish pond Pipe N take 15 d

It takes pipe A 10 days to fill a fish pond. Pipe N take 15 days. How long would it take both piper together fill the pond?

Solution

Work done by pipe A in 1 day=1/10

Work done by pipe B in 1 day= 1/15

Work done in 1 hour when they both work together=1/10 + 1/15 = 5/30=1/6

So when they both work together,the pond will filled in 6 days