Two pipes can fill a tank in 6hour the large pipe works twice as fast as the smaller pipe.how long would it take each pipe to fill the tank if they worked separately ?

Let's assume that the smaller pipe can fill the tank in x hours.

Since the larger pipe works twice as fast as the smaller pipe, it can fill the tank in x/2 hours.

Together, the two pipes can fill the tank in 6 hours.

Using the formula:
1/(x/2) + 1/x = 1/6

Multiplying through by 6x, we get:
6 + 12 = x/2

18 = x/2

x = 36

Therefore, it would take the smaller pipe 36 hours to fill the tank if it worked separately.

The larger pipe, which works twice as fast, would take 36/2 = 18 hours to fill the tank if it worked separately.