The first pipe, working separately, fills the pool with water in 2 hours, and the second pipe in 6 hours. At first, both pipes

The first pipe, working separately, fills the pool with water in 2 hours, and the second pipe in 6 hours. At first, both pipes worked for 30 minutes. How long does it take for only the second pipe to complete the filling of the pool? Write your answer in hours.

the first pipe fills 1/2 in an hour, but since we have half an hour, during this time it will fill 1/4
the second pipe fills 1/6 in an hour, and 1/12 in half an hour
1 is a fully filled pool
1- (1/4 + 1/12) = 1- (3/12 + 1/12) = 1-4 / 12 = 8/12-so much remains to fill the second pipe
8/12: 1/6 = 8/12 * 6/1 = 8/2 = 4 (h) – it takes time for only the second pipe to complete the filling of the pool
Answer: 4 hours